Adding upstream version 115.7.0esr.upstream/115.7.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

27 files changed, 5799 insertions, 0 deletions

diff --git a/third_party/python/multidict/CHANGES.rst b/third_party/python/multidict/CHANGES.rst
new file mode 100644
index 0000000000..c10b8c297a
--- /dev/null
+++ b/third_party/python/multidict/CHANGES.rst
@@ -0,0 +1,255 @@
+=========
+Changelog
+=========
+
+..
+    You should *NOT* be adding new change log entries to this file, this
+    file is managed by towncrier. You *may* edit previous change logs to
+    fix problems like typo corrections or such.
+    To add a new change log entry, please see
+    https://pip.pypa.io/en/latest/development/#adding-a-news-entry
+    we named the news folder "changes".
+
+    WARNING: Don't drop the next directive!
+
+.. towncrier release notes start
+
+5.1.0 (2020-12-03)
+==================
+
+Features
+--------
+
+- Support ``GenericAliases`` (``MultiDict[str]``) for Python 3.9+
+  `#553 <https://github.com/aio-libs/multidict/issues/553>`_
+
+
+Bugfixes
+--------
+
+- Synchronize the declared supported Python versions in ``setup.py`` with actually supported and tested ones.
+  `#552 <https://github.com/aio-libs/multidict/issues/552>`_
+
+
+----
+
+
+5.0.1 (2020-11-14)
+==================
+
+Bugfixes
+--------
+
+- Provide x86 Windows wheels
+  `#550 <https://github.com/aio-libs/multidict/issues/550>`_
+
+
+----
+
+
+5.0.0 (2020-10-12)
+==================
+
+Features
+--------
+
+- Provide wheels for ``aarch64``, ``i686``, ``ppc64le``, ``s390x`` architectures on Linux
+  as well as ``x86_64``.
+  `#500 <https://github.com/aio-libs/multidict/issues/500>`_
+- Provide wheels for Python 3.9.
+  `#534 <https://github.com/aio-libs/multidict/issues/534>`_
+
+Removal
+-------
+
+- Drop Python 3.5 support; Python 3.6 is the minimal supported Python version.
+
+Misc
+----
+
+- `#503 <https://github.com/aio-libs/multidict/issues/503>`_
+
+
+----
+
+
+4.7.6 (2020-05-15)
+==================
+
+Bugfixes
+--------
+
+- Fixed an issue with some versions of the ``wheel`` dist
+  failing because of being unable to detect the license file.
+  `#481 <https://github.com/aio-libs/multidict/issues/481>`_
+
+
+----
+
+
+4.7.5 (2020-02-21)
+==================
+
+Bugfixes
+--------
+
+- Fixed creating and updating of MultiDict from a sequence of pairs and keyword
+  arguments. Previously passing a list argument modified it inplace, and other sequences
+  caused an error.
+  `#457 <https://github.com/aio-libs/multidict/issues/457>`_
+- Fixed comparing with mapping: an exception raised in the
+  :py:func:`~object.__len__` method caused raising a SyntaxError.
+  `#459 <https://github.com/aio-libs/multidict/issues/459>`_
+- Fixed comparing with mapping: all exceptions raised in the
+  :py:func:`~object.__getitem__` method were silenced.
+  `#460 <https://github.com/aio-libs/multidict/issues/460>`_
+
+
+----
+
+
+4.7.4 (2020-01-11)
+==================
+
+Bugfixes
+--------
+
+- ``MultiDict.iter`` fix memory leak when used iterator over
+  :py:mod:`multidict` instance.
+  `#452 <https://github.com/aio-libs/multidict/issues/452>`_
+
+
+----
+
+
+4.7.3 (2019-12-30)
+==================
+
+Features
+--------
+
+- Implement ``__sizeof__`` function to correctly calculate all internal structures size.
+  `#444 <https://github.com/aio-libs/multidict/issues/444>`_
+- Expose ``getversion()`` function.
+  `#451 <https://github.com/aio-libs/multidict/issues/451>`_
+
+
+Bugfixes
+--------
+
+- Fix crashes in ``popone``/``popall`` when default is returned.
+  `#450 <https://github.com/aio-libs/multidict/issues/450>`_
+
+
+Improved Documentation
+----------------------
+
+- Corrected the documentation for ``MultiDict.extend()``
+  `#446 <https://github.com/aio-libs/multidict/issues/446>`_
+
+
+----
+
+
+4.7.2 (2019-12-20)
+==================
+
+Bugfixes
+--------
+
+- Fix crashing when multidict is used pyinstaller
+  `#432 <https://github.com/aio-libs/multidict/issues/432>`_
+- Fix typing for :py:meth:`CIMultiDict.copy`
+  `#434 <https://github.com/aio-libs/multidict/issues/434>`_
+- Fix memory leak in ``MultiDict.copy()``
+  `#443 <https://github.com/aio-libs/multidict/issues/443>`_
+
+
+----
+
+
+4.7.1 (2019-12-12)
+==================
+
+Bugfixes
+--------
+
+- :py:meth:`CIMultiDictProxy.copy` return object type
+  :py:class:`multidict._multidict.CIMultiDict`
+  `#427 <https://github.com/aio-libs/multidict/issues/427>`_
+- Make :py:class:`CIMultiDict` subclassable again
+  `#416 <https://github.com/aio-libs/multidict/issues/416>`_
+- Fix regression, multidict can be constructed from arbitrary iterable of pairs again.
+  `#418 <https://github.com/aio-libs/multidict/issues/418>`_
+- :py:meth:`CIMultiDict.add` may be called with keyword arguments
+  `#421 <https://github.com/aio-libs/multidict/issues/421>`_
+
+
+Improved Documentation
+----------------------
+
+- Mention ``MULTIDICT_NO_EXTENSIONS`` environment variable in docs.
+  `#393 <https://github.com/aio-libs/multidict/issues/393>`_
+- Document the fact that ``istr`` preserves the casing of argument untouched but uses internal lower-cased copy for keys comparison.
+  `#419 <https://github.com/aio-libs/multidict/issues/419>`_
+
+
+----
+
+
+4.7.0 (2019-12-10)
+==================
+
+Features
+--------
+
+- Replace Cython optimization with pure C
+  `#249 <https://github.com/aio-libs/multidict/issues/249>`_
+- Implement ``__length_hint__()`` for iterators
+  `#310 <https://github.com/aio-libs/multidict/issues/310>`_
+- Support the MultiDict[str] generic specialization in the runtime.
+  `#392 <https://github.com/aio-libs/multidict/issues/392>`_
+- Embed pair_list_t structure into MultiDict Python object
+  `#395 <https://github.com/aio-libs/multidict/issues/395>`_
+- Embed multidict pairs for small dictionaries to amortize the memory usage.
+  `#396 <https://github.com/aio-libs/multidict/issues/396>`_
+- Support weak references to C Extension classes.
+  `#399 <https://github.com/aio-libs/multidict/issues/399>`_
+- Add docstrings to provided classes.
+  `#400 <https://github.com/aio-libs/multidict/issues/400>`_
+- Merge ``multidict._istr`` back with ``multidict._multidict``.
+  `#409 <https://github.com/aio-libs/multidict/issues/409>`_
+
+
+Bugfixes
+--------
+
+- Explicitly call ``tp_free`` slot on deallocation.
+  `#407 <https://github.com/aio-libs/multidict/issues/407>`_
+- Return class from __class_getitem__ to simplify subclassing
+  `#413 <https://github.com/aio-libs/multidict/issues/413>`_
+
+
+----
+
+
+4.6.1 (2019-11-21)
+====================
+
+Bugfixes
+--------
+
+- Fix PyPI link for GitHub Issues badge.
+  `#391 <https://github.com/aio-libs/aiohttp/issues/391>`_
+
+4.6.0 (2019-11-20)
+====================
+
+Bugfixes
+--------
+
+- Fix GC object tracking.
+  `#314 <https://github.com/aio-libs/aiohttp/issues/314>`_
+- Preserve the case of `istr` strings.
+  `#374 <https://github.com/aio-libs/aiohttp/issues/374>`_
+- Generate binary wheels for Python 3.8.
diff --git a/third_party/python/multidict/LICENSE b/third_party/python/multidict/LICENSE
new file mode 100644
index 0000000000..99a9e21af0
--- /dev/null
+++ b/third_party/python/multidict/LICENSE
@@ -0,0 +1,201 @@
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+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
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+      incidental, or consequential damages of any character arising as a
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+      on Your own behalf and on Your sole responsibility, not on behalf
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+   END OF TERMS AND CONDITIONS
+
+   APPENDIX: How to apply the Apache License to your work.
+
+      To apply the Apache License to your work, attach the following
+      boilerplate notice, with the fields enclosed by brackets "{}"
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+   you may not use this file except in compliance with the License.
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diff --git a/third_party/python/multidict/MANIFEST.in b/third_party/python/multidict/MANIFEST.in
new file mode 100644
index 0000000000..c39a12f0b6
--- /dev/null
+++ b/third_party/python/multidict/MANIFEST.in
@@ -0,0 +1,14 @@
+include LICENSE
+include CHANGES.rst
+include README.rst
+include Makefile
+graft multidict
+graft docs
+graft tests
+global-exclude *.pyc
+include multidict/*.c
+exclude multidict/_multidict.html
+exclude multidict/*.so
+exclude multidict/*.pyd
+exclude multidict/*.pyd
+prune docs/_build
diff --git a/third_party/python/multidict/Makefile b/third_party/python/multidict/Makefile
new file mode 100644
index 0000000000..ca0562b043
--- /dev/null
+++ b/third_party/python/multidict/Makefile
@@ -0,0 +1,108 @@
+# Some simple testing tasks (sorry, UNIX only).
+.PHONY: all build flake test vtest cov clean doc mypy
+
+
+PYXS = $(wildcard multidict/*.pyx)
+SRC = multidict tests setup.py
+
+all: test
+
+.install-deps: $(shell find requirements -type f)
+	pip install -r requirements/dev.txt
+	@touch .install-deps
+
+.flake: .install-deps $(shell find multidict -type f) \
+                      $(shell find tests -type f)
+	flake8 multidict tests
+	@if ! isort --check multidict tests; then \
+            echo "Import sort errors, run 'make fmt' to fix them!!!"; \
+            isort --diff --check multidict tests; \
+            false; \
+	fi
+	@touch .flake
+
+
+isort-check:
+	@if ! isort --check $(SRC); then \
+            echo "Import sort errors, run 'make fmt' to fix them!!!"; \
+            isort --diff --check $(SRC); \
+            false; \
+	fi
+
+flake8:
+	flake8 $(SRC)
+
+black-check:
+	@if ! isort --check $(SRC); then \
+            echo "black errors, run 'make fmt' to fix them!!!"; \
+	    black -t py35 --diff --check $(SRC); \
+            false; \
+	fi
+
+mypy:
+	mypy --show-error-codes multidict tests
+
+lint: flake8 black-check mypy isort-check check_changes
+
+fmt:
+	black -t py35 $(SRC)
+	isort $(SRC)
+
+check_changes:
+	./tools/check_changes.py
+
+.develop: .install-deps $(shell find multidict -type f) .flake check_changes mypy
+	pip install -e .
+	@touch .develop
+
+test: .develop
+	@pytest -q
+
+vtest: .develop
+	@pytest -s -v
+
+cov-dev: .develop
+	@pytest --cov-report=html
+	@echo "open file://`pwd`/htmlcov/index.html"
+
+cov-ci-run: .develop
+	@echo "Regular run"
+	@pytest --cov-report=html
+
+cov-dev-full: cov-ci-run
+	@echo "open file://`pwd`/htmlcov/index.html"
+
+doc:
+	@make -C docs html SPHINXOPTS="-W -E"
+	@echo "open file://`pwd`/docs/_build/html/index.html"
+
+doc-spelling:
+	@make -C docs spelling SPHINXOPTS="-W -E"
+
+install:
+	@pip install -U 'pip'
+	@pip install -Ur requirements/dev.txt
+
+install-dev: .develop
+
+
+clean:
+	rm -rf `find . -name __pycache__`
+	rm -f `find . -type f -name '*.py[co]' `
+	rm -f `find . -type f -name '*~' `
+	rm -f `find . -type f -name '.*~' `
+	rm -f `find . -type f -name '@*' `
+	rm -f `find . -type f -name '#*#' `
+	rm -f `find . -type f -name '*.orig' `
+	rm -f `find . -type f -name '*.rej' `
+	rm -f .coverage
+	rm -rf coverage
+	rm -rf build
+	rm -rf cover
+	rm -rf htmlcov
+	make -C docs clean SPHINXBUILD=false
+	python3 setup.py clean
+	rm -f multidict/*.html
+	rm -f multidict/*.so
+	rm -f multidict/*.pyd
+	rm -rf .tox
diff --git a/third_party/python/multidict/PKG-INFO b/third_party/python/multidict/PKG-INFO
new file mode 100644
index 0000000000..bbd4864947
--- /dev/null
+++ b/third_party/python/multidict/PKG-INFO
@@ -0,0 +1,128 @@
+Metadata-Version: 1.2
+Name: multidict
+Version: 5.1.0
+Summary: multidict implementation
+Home-page: https://github.com/aio-libs/multidict
+Author: Andrew Svetlov
+Author-email: andrew.svetlov@gmail.com
+License: Apache 2
+Project-URL: Chat: Gitter, https://gitter.im/aio-libs/Lobby
+Project-URL: CI: Azure Pipelines, https://dev.azure.com/aio-libs/multidict/_build
+Project-URL: Coverage: codecov, https://codecov.io/github/aio-libs/multidict
+Project-URL: Docs: RTD, https://multidict.readthedocs.io
+Project-URL: GitHub: issues, https://github.com/aio-libs/multidict/issues
+Project-URL: GitHub: repo, https://github.com/aio-libs/multidict
+Description: =========
+        multidict
+        =========
+        
+        .. image:: https://github.com/aio-libs/multidict/workflows/CI/badge.svg
+           :target: https://github.com/aio-libs/multidict/actions?query=workflow%3ACI
+           :alt: GitHub status for master branch
+        
+        .. image:: https://codecov.io/gh/aio-libs/multidict/branch/master/graph/badge.svg
+           :target: https://codecov.io/gh/aio-libs/multidict
+           :alt: Coverage metrics
+        
+        .. image:: https://img.shields.io/pypi/v/multidict.svg
+           :target: https://pypi.org/project/multidict
+           :alt: PyPI
+        
+        .. image:: https://readthedocs.org/projects/multidict/badge/?version=latest
+           :target: http://multidict.readthedocs.org/en/latest/?badge=latest
+           :alt: Documentationb
+        
+        .. image:: https://img.shields.io/pypi/pyversions/multidict.svg
+           :target: https://pypi.org/project/multidict
+           :alt: Python versions
+        
+        .. image:: https://badges.gitter.im/Join%20Chat.svg
+           :target: https://gitter.im/aio-libs/Lobby
+           :alt: Chat on Gitter
+        
+        Multidict is dict-like collection of *key-value pairs* where key
+        might be occurred more than once in the container.
+        
+        Introduction
+        ------------
+        
+        *HTTP Headers* and *URL query string* require specific data structure:
+        *multidict*. It behaves mostly like a regular ``dict`` but it may have
+        several *values* for the same *key* and *preserves insertion ordering*.
+        
+        The *key* is ``str`` (or ``istr`` for case-insensitive dictionaries).
+        
+        ``multidict`` has four multidict classes:
+        ``MultiDict``, ``MultiDictProxy``, ``CIMultiDict``
+        and ``CIMultiDictProxy``.
+        
+        Immutable proxies (``MultiDictProxy`` and
+        ``CIMultiDictProxy``) provide a dynamic view for the
+        proxied multidict, the view reflects underlying collection changes. They
+        implement the ``collections.abc.Mapping`` interface.
+        
+        Regular mutable (``MultiDict`` and ``CIMultiDict``) classes
+        implement ``collections.abc.MutableMapping`` and allows to change
+        their own content.
+        
+        
+        *Case insensitive* (``CIMultiDict`` and
+        ``CIMultiDictProxy``) ones assume the *keys* are case
+        insensitive, e.g.::
+        
+           >>> dct = CIMultiDict(key='val')
+           >>> 'Key' in dct
+           True
+           >>> dct['Key']
+           'val'
+        
+        *Keys* should be ``str`` or ``istr`` instances.
+        
+        The library has optional C Extensions for sake of speed.
+        
+        
+        License
+        -------
+        
+        Apache 2
+        
+        Library Installation
+        --------------------
+        
+        .. code-block:: bash
+        
+           $ pip install multidict
+        
+        The library is Python 3 only!
+        
+        PyPI contains binary wheels for Linux, Windows and MacOS.  If you want to install
+        ``multidict`` on another operation system (or *Alpine Linux* inside a Docker) the
+        Tarball will be used to compile the library from sources.  It requires C compiler and
+        Python headers installed.
+        
+        To skip the compilation please use `MULTIDICT_NO_EXTENSIONS` environment variable,
+        e.g.:
+        
+        .. code-block:: bash
+        
+           $ MULTIDICT_NO_EXTENSIONS=1 pip install multidict
+        
+        Please note, Pure Python (uncompiled) version is about 20-50 times slower depending on
+        the usage scenario!!!
+        
+        
+        
+        Changelog
+        ---------
+        See `RTD page <http://multidict.readthedocs.org/en/latest/changes.html>`_.
+Platform: UNKNOWN
+Classifier: License :: OSI Approved :: Apache Software License
+Classifier: Intended Audience :: Developers
+Classifier: Programming Language :: Python
+Classifier: Programming Language :: Python :: 3
+Classifier: Programming Language :: Python :: 3.6
+Classifier: Programming Language :: Python :: 3.7
+Classifier: Programming Language :: Python :: 3.8
+Classifier: Programming Language :: Python :: 3.9
+Classifier: Development Status :: 5 - Production/Stable
+Requires-Python: >=3.6
diff --git a/third_party/python/multidict/README.rst b/third_party/python/multidict/README.rst
new file mode 100644
index 0000000000..e78e5065c2
--- /dev/null
+++ b/third_party/python/multidict/README.rst
@@ -0,0 +1,103 @@
+=========
+multidict
+=========
+
+.. image:: https://github.com/aio-libs/multidict/workflows/CI/badge.svg
+   :target: https://github.com/aio-libs/multidict/actions?query=workflow%3ACI
+   :alt: GitHub status for master branch
+
+.. image:: https://codecov.io/gh/aio-libs/multidict/branch/master/graph/badge.svg
+   :target: https://codecov.io/gh/aio-libs/multidict
+   :alt: Coverage metrics
+
+.. image:: https://img.shields.io/pypi/v/multidict.svg
+   :target: https://pypi.org/project/multidict
+   :alt: PyPI
+
+.. image:: https://readthedocs.org/projects/multidict/badge/?version=latest
+   :target: http://multidict.readthedocs.org/en/latest/?badge=latest
+   :alt: Documentationb
+
+.. image:: https://img.shields.io/pypi/pyversions/multidict.svg
+   :target: https://pypi.org/project/multidict
+   :alt: Python versions
+
+.. image:: https://badges.gitter.im/Join%20Chat.svg
+   :target: https://gitter.im/aio-libs/Lobby
+   :alt: Chat on Gitter
+
+Multidict is dict-like collection of *key-value pairs* where key
+might be occurred more than once in the container.
+
+Introduction
+------------
+
+*HTTP Headers* and *URL query string* require specific data structure:
+*multidict*. It behaves mostly like a regular ``dict`` but it may have
+several *values* for the same *key* and *preserves insertion ordering*.
+
+The *key* is ``str`` (or ``istr`` for case-insensitive dictionaries).
+
+``multidict`` has four multidict classes:
+``MultiDict``, ``MultiDictProxy``, ``CIMultiDict``
+and ``CIMultiDictProxy``.
+
+Immutable proxies (``MultiDictProxy`` and
+``CIMultiDictProxy``) provide a dynamic view for the
+proxied multidict, the view reflects underlying collection changes. They
+implement the ``collections.abc.Mapping`` interface.
+
+Regular mutable (``MultiDict`` and ``CIMultiDict``) classes
+implement ``collections.abc.MutableMapping`` and allows to change
+their own content.
+
+
+*Case insensitive* (``CIMultiDict`` and
+``CIMultiDictProxy``) ones assume the *keys* are case
+insensitive, e.g.::
+
+   >>> dct = CIMultiDict(key='val')
+   >>> 'Key' in dct
+   True
+   >>> dct['Key']
+   'val'
+
+*Keys* should be ``str`` or ``istr`` instances.
+
+The library has optional C Extensions for sake of speed.
+
+
+License
+-------
+
+Apache 2
+
+Library Installation
+--------------------
+
+.. code-block:: bash
+
+   $ pip install multidict
+
+The library is Python 3 only!
+
+PyPI contains binary wheels for Linux, Windows and MacOS.  If you want to install
+``multidict`` on another operation system (or *Alpine Linux* inside a Docker) the
+Tarball will be used to compile the library from sources.  It requires C compiler and
+Python headers installed.
+
+To skip the compilation please use `MULTIDICT_NO_EXTENSIONS` environment variable,
+e.g.:
+
+.. code-block:: bash
+
+   $ MULTIDICT_NO_EXTENSIONS=1 pip install multidict
+
+Please note, Pure Python (uncompiled) version is about 20-50 times slower depending on
+the usage scenario!!!
+
+
+
+Changelog
+---------
+See `RTD page <http://multidict.readthedocs.org/en/latest/changes.html>`_.
diff --git a/third_party/python/multidict/multidict.egg-info/PKG-INFO b/third_party/python/multidict/multidict.egg-info/PKG-INFO
new file mode 100644
index 0000000000..bbd4864947
--- /dev/null
+++ b/third_party/python/multidict/multidict.egg-info/PKG-INFO
@@ -0,0 +1,128 @@
+Metadata-Version: 1.2
+Name: multidict
+Version: 5.1.0
+Summary: multidict implementation
+Home-page: https://github.com/aio-libs/multidict
+Author: Andrew Svetlov
+Author-email: andrew.svetlov@gmail.com
+License: Apache 2
+Project-URL: Chat: Gitter, https://gitter.im/aio-libs/Lobby
+Project-URL: CI: Azure Pipelines, https://dev.azure.com/aio-libs/multidict/_build
+Project-URL: Coverage: codecov, https://codecov.io/github/aio-libs/multidict
+Project-URL: Docs: RTD, https://multidict.readthedocs.io
+Project-URL: GitHub: issues, https://github.com/aio-libs/multidict/issues
+Project-URL: GitHub: repo, https://github.com/aio-libs/multidict
+Description: =========
+        multidict
+        =========
+        
+        .. image:: https://github.com/aio-libs/multidict/workflows/CI/badge.svg
+           :target: https://github.com/aio-libs/multidict/actions?query=workflow%3ACI
+           :alt: GitHub status for master branch
+        
+        .. image:: https://codecov.io/gh/aio-libs/multidict/branch/master/graph/badge.svg
+           :target: https://codecov.io/gh/aio-libs/multidict
+           :alt: Coverage metrics
+        
+        .. image:: https://img.shields.io/pypi/v/multidict.svg
+           :target: https://pypi.org/project/multidict
+           :alt: PyPI
+        
+        .. image:: https://readthedocs.org/projects/multidict/badge/?version=latest
+           :target: http://multidict.readthedocs.org/en/latest/?badge=latest
+           :alt: Documentationb
+        
+        .. image:: https://img.shields.io/pypi/pyversions/multidict.svg
+           :target: https://pypi.org/project/multidict
+           :alt: Python versions
+        
+        .. image:: https://badges.gitter.im/Join%20Chat.svg
+           :target: https://gitter.im/aio-libs/Lobby
+           :alt: Chat on Gitter
+        
+        Multidict is dict-like collection of *key-value pairs* where key
+        might be occurred more than once in the container.
+        
+        Introduction
+        ------------
+        
+        *HTTP Headers* and *URL query string* require specific data structure:
+        *multidict*. It behaves mostly like a regular ``dict`` but it may have
+        several *values* for the same *key* and *preserves insertion ordering*.
+        
+        The *key* is ``str`` (or ``istr`` for case-insensitive dictionaries).
+        
+        ``multidict`` has four multidict classes:
+        ``MultiDict``, ``MultiDictProxy``, ``CIMultiDict``
+        and ``CIMultiDictProxy``.
+        
+        Immutable proxies (``MultiDictProxy`` and
+        ``CIMultiDictProxy``) provide a dynamic view for the
+        proxied multidict, the view reflects underlying collection changes. They
+        implement the ``collections.abc.Mapping`` interface.
+        
+        Regular mutable (``MultiDict`` and ``CIMultiDict``) classes
+        implement ``collections.abc.MutableMapping`` and allows to change
+        their own content.
+        
+        
+        *Case insensitive* (``CIMultiDict`` and
+        ``CIMultiDictProxy``) ones assume the *keys* are case
+        insensitive, e.g.::
+        
+           >>> dct = CIMultiDict(key='val')
+           >>> 'Key' in dct
+           True
+           >>> dct['Key']
+           'val'
+        
+        *Keys* should be ``str`` or ``istr`` instances.
+        
+        The library has optional C Extensions for sake of speed.
+        
+        
+        License
+        -------
+        
+        Apache 2
+        
+        Library Installation
+        --------------------
+        
+        .. code-block:: bash
+        
+           $ pip install multidict
+        
+        The library is Python 3 only!
+        
+        PyPI contains binary wheels for Linux, Windows and MacOS.  If you want to install
+        ``multidict`` on another operation system (or *Alpine Linux* inside a Docker) the
+        Tarball will be used to compile the library from sources.  It requires C compiler and
+        Python headers installed.
+        
+        To skip the compilation please use `MULTIDICT_NO_EXTENSIONS` environment variable,
+        e.g.:
+        
+        .. code-block:: bash
+        
+           $ MULTIDICT_NO_EXTENSIONS=1 pip install multidict
+        
+        Please note, Pure Python (uncompiled) version is about 20-50 times slower depending on
+        the usage scenario!!!
+        
+        
+        
+        Changelog
+        ---------
+        See `RTD page <http://multidict.readthedocs.org/en/latest/changes.html>`_.
+Platform: UNKNOWN
+Classifier: License :: OSI Approved :: Apache Software License
+Classifier: Intended Audience :: Developers
+Classifier: Programming Language :: Python
+Classifier: Programming Language :: Python :: 3
+Classifier: Programming Language :: Python :: 3.6
+Classifier: Programming Language :: Python :: 3.7
+Classifier: Programming Language :: Python :: 3.8
+Classifier: Programming Language :: Python :: 3.9
+Classifier: Development Status :: 5 - Production/Stable
+Requires-Python: >=3.6
diff --git a/third_party/python/multidict/multidict.egg-info/SOURCES.txt b/third_party/python/multidict/multidict.egg-info/SOURCES.txt
new file mode 100644
index 0000000000..6c6257ea9b
--- /dev/null
+++ b/third_party/python/multidict/multidict.egg-info/SOURCES.txt
@@ -0,0 +1,71 @@
+CHANGES.rst
+LICENSE
+MANIFEST.in
+Makefile
+README.rst
+pyproject.toml
+setup.cfg
+setup.py
+docs/Makefile
+docs/benchmark.rst
+docs/changes.rst
+docs/conf.py
+docs/index.rst
+docs/make.bat
+docs/multidict.rst
+docs/spelling_wordlist.txt
+multidict/__init__.py
+multidict/__init__.pyi
+multidict/_abc.py
+multidict/_compat.py
+multidict/_multidict.c
+multidict/_multidict_base.py
+multidict/_multidict_py.py
+multidict/py.typed
+multidict.egg-info/PKG-INFO
+multidict.egg-info/SOURCES.txt
+multidict.egg-info/dependency_links.txt
+multidict.egg-info/top_level.txt
+multidict/_multilib/defs.h
+multidict/_multilib/dict.h
+multidict/_multilib/istr.h
+multidict/_multilib/iter.h
+multidict/_multilib/pair_list.h
+multidict/_multilib/views.h
+tests/cimultidict.pickle.0
+tests/cimultidict.pickle.1
+tests/cimultidict.pickle.2
+tests/cimultidict.pickle.3
+tests/cimultidict.pickle.4
+tests/cimultidict.pickle.5
+tests/conftest.py
+tests/gen_pickles.py
+tests/multidict.pickle.0
+tests/multidict.pickle.1
+tests/multidict.pickle.2
+tests/multidict.pickle.3
+tests/multidict.pickle.4
+tests/multidict.pickle.5
+tests/pycimultidict.pickle.0
+tests/pycimultidict.pickle.1
+tests/pycimultidict.pickle.2
+tests/pycimultidict.pickle.3
+tests/pycimultidict.pickle.4
+tests/pycimultidict.pickle.5
+tests/pymultidict.pickle.0
+tests/pymultidict.pickle.1
+tests/pymultidict.pickle.2
+tests/pymultidict.pickle.3
+tests/pymultidict.pickle.4
+tests/pymultidict.pickle.5
+tests/test_abc.py
+tests/test_copy.py
+tests/test_guard.py
+tests/test_istr.py
+tests/test_multidict.py
+tests/test_mutable_multidict.py
+tests/test_mypy.py
+tests/test_pickle.py
+tests/test_types.py
+tests/test_update.py
+tests/test_version.py
\ No newline at end of file
diff --git a/third_party/python/multidict/multidict.egg-info/dependency_links.txt b/third_party/python/multidict/multidict.egg-info/dependency_links.txt
new file mode 100644
index 0000000000..8b13789179
--- /dev/null
+++ b/third_party/python/multidict/multidict.egg-info/dependency_links.txt
@@ -0,0 +1 @@
+
diff --git a/third_party/python/multidict/multidict.egg-info/top_level.txt b/third_party/python/multidict/multidict.egg-info/top_level.txt
new file mode 100644
index 0000000000..afcecdff08
--- /dev/null
+++ b/third_party/python/multidict/multidict.egg-info/top_level.txt
@@ -0,0 +1 @@
+multidict
diff --git a/third_party/python/multidict/multidict/__init__.py b/third_party/python/multidict/multidict/__init__.py
new file mode 100644
index 0000000000..6b091d1431
--- /dev/null
+++ b/third_party/python/multidict/multidict/__init__.py
@@ -0,0 +1,48 @@
+"""Multidict implementation.
+
+HTTP Headers and URL query string require specific data structure:
+multidict. It behaves mostly like a dict but it can have
+several values for the same key.
+"""
+
+from ._abc import MultiMapping, MutableMultiMapping
+from ._compat import USE_CYTHON_EXTENSIONS
+
+__all__ = (
+    "MultiMapping",
+    "MutableMultiMapping",
+    "MultiDictProxy",
+    "CIMultiDictProxy",
+    "MultiDict",
+    "CIMultiDict",
+    "upstr",
+    "istr",
+    "getversion",
+)
+
+__version__ = "5.1.0"
+
+
+try:
+    if not USE_CYTHON_EXTENSIONS:
+        raise ImportError
+    from ._multidict import (
+        CIMultiDict,
+        CIMultiDictProxy,
+        MultiDict,
+        MultiDictProxy,
+        getversion,
+        istr,
+    )
+except ImportError:  # pragma: no cover
+    from ._multidict_py import (
+        CIMultiDict,
+        CIMultiDictProxy,
+        MultiDict,
+        MultiDictProxy,
+        getversion,
+        istr,
+    )
+
+
+upstr = istr
diff --git a/third_party/python/multidict/multidict/__init__.pyi b/third_party/python/multidict/multidict/__init__.pyi
new file mode 100644
index 0000000000..24ba63054b
--- /dev/null
+++ b/third_party/python/multidict/multidict/__init__.pyi
@@ -0,0 +1,152 @@
+import abc
+from typing import (
+    Dict,
+    Generic,
+    Iterable,
+    Iterator,
+    List,
+    Mapping,
+    MutableMapping,
+    Tuple,
+    TypeVar,
+    Union,
+    overload,
+)
+
+class istr(str): ...
+
+upstr = istr
+
+_S = Union[str, istr]
+
+_T = TypeVar("_T")
+
+_T_co = TypeVar("_T_co", covariant=True)
+
+_D = TypeVar("_D")
+
+class MultiMapping(Mapping[_S, _T_co]):
+    @overload
+    @abc.abstractmethod
+    def getall(self, key: _S) -> List[_T_co]: ...
+    @overload
+    @abc.abstractmethod
+    def getall(self, key: _S, default: _D) -> Union[List[_T_co], _D]: ...
+    @overload
+    @abc.abstractmethod
+    def getone(self, key: _S) -> _T_co: ...
+    @overload
+    @abc.abstractmethod
+    def getone(self, key: _S, default: _D) -> Union[_T_co, _D]: ...
+
+_Arg = Union[Mapping[_S, _T], Dict[_S, _T], MultiMapping[_T], Iterable[Tuple[_S, _T]]]
+
+class MutableMultiMapping(MultiMapping[_T], MutableMapping[_S, _T], Generic[_T]):
+    @abc.abstractmethod
+    def add(self, key: _S, value: _T) -> None: ...
+    @abc.abstractmethod
+    def extend(self, arg: _Arg[_T] = ..., **kwargs: _T) -> None: ...
+    @overload
+    @abc.abstractmethod
+    def popone(self, key: _S) -> _T: ...
+    @overload
+    @abc.abstractmethod
+    def popone(self, key: _S, default: _D) -> Union[_T, _D]: ...
+    @overload
+    @abc.abstractmethod
+    def popall(self, key: _S) -> List[_T]: ...
+    @overload
+    @abc.abstractmethod
+    def popall(self, key: _S, default: _D) -> Union[List[_T], _D]: ...
+
+class MultiDict(MutableMultiMapping[_T], Generic[_T]):
+    def __init__(self, arg: _Arg[_T] = ..., **kwargs: _T) -> None: ...
+    def copy(self) -> MultiDict[_T]: ...
+    def __getitem__(self, k: _S) -> _T: ...
+    def __setitem__(self, k: _S, v: _T) -> None: ...
+    def __delitem__(self, v: _S) -> None: ...
+    def __iter__(self) -> Iterator[_S]: ...
+    def __len__(self) -> int: ...
+    @overload
+    def getall(self, key: _S) -> List[_T]: ...
+    @overload
+    def getall(self, key: _S, default: _D) -> Union[List[_T], _D]: ...
+    @overload
+    def getone(self, key: _S) -> _T: ...
+    @overload
+    def getone(self, key: _S, default: _D) -> Union[_T, _D]: ...
+    def add(self, key: _S, value: _T) -> None: ...
+    def extend(self, arg: _Arg[_T] = ..., **kwargs: _T) -> None: ...
+    @overload
+    def popone(self, key: _S) -> _T: ...
+    @overload
+    def popone(self, key: _S, default: _D) -> Union[_T, _D]: ...
+    @overload
+    def popall(self, key: _S) -> List[_T]: ...
+    @overload
+    def popall(self, key: _S, default: _D) -> Union[List[_T], _D]: ...
+
+class CIMultiDict(MutableMultiMapping[_T], Generic[_T]):
+    def __init__(self, arg: _Arg[_T] = ..., **kwargs: _T) -> None: ...
+    def copy(self) -> CIMultiDict[_T]: ...
+    def __getitem__(self, k: _S) -> _T: ...
+    def __setitem__(self, k: _S, v: _T) -> None: ...
+    def __delitem__(self, v: _S) -> None: ...
+    def __iter__(self) -> Iterator[_S]: ...
+    def __len__(self) -> int: ...
+    @overload
+    def getall(self, key: _S) -> List[_T]: ...
+    @overload
+    def getall(self, key: _S, default: _D) -> Union[List[_T], _D]: ...
+    @overload
+    def getone(self, key: _S) -> _T: ...
+    @overload
+    def getone(self, key: _S, default: _D) -> Union[_T, _D]: ...
+    def add(self, key: _S, value: _T) -> None: ...
+    def extend(self, arg: _Arg[_T] = ..., **kwargs: _T) -> None: ...
+    @overload
+    def popone(self, key: _S) -> _T: ...
+    @overload
+    def popone(self, key: _S, default: _D) -> Union[_T, _D]: ...
+    @overload
+    def popall(self, key: _S) -> List[_T]: ...
+    @overload
+    def popall(self, key: _S, default: _D) -> Union[List[_T], _D]: ...
+
+class MultiDictProxy(MultiMapping[_T], Generic[_T]):
+    def __init__(
+        self, arg: Union[MultiMapping[_T], MutableMultiMapping[_T]]
+    ) -> None: ...
+    def copy(self) -> MultiDict[_T]: ...
+    def __getitem__(self, k: _S) -> _T: ...
+    def __iter__(self) -> Iterator[_S]: ...
+    def __len__(self) -> int: ...
+    @overload
+    def getall(self, key: _S) -> List[_T]: ...
+    @overload
+    def getall(self, key: _S, default: _D) -> Union[List[_T], _D]: ...
+    @overload
+    def getone(self, key: _S) -> _T: ...
+    @overload
+    def getone(self, key: _S, default: _D) -> Union[_T, _D]: ...
+
+class CIMultiDictProxy(MultiMapping[_T], Generic[_T]):
+    def __init__(
+        self, arg: Union[MultiMapping[_T], MutableMultiMapping[_T]]
+    ) -> None: ...
+    def __getitem__(self, k: _S) -> _T: ...
+    def __iter__(self) -> Iterator[_S]: ...
+    def __len__(self) -> int: ...
+    @overload
+    def getall(self, key: _S) -> List[_T]: ...
+    @overload
+    def getall(self, key: _S, default: _D) -> Union[List[_T], _D]: ...
+    @overload
+    def getone(self, key: _S) -> _T: ...
+    @overload
+    def getone(self, key: _S, default: _D) -> Union[_T, _D]: ...
+    def copy(self) -> CIMultiDict[_T]: ...
+
+def getversion(
+    md: Union[MultiDict[_T], CIMultiDict[_T], MultiDictProxy[_T], CIMultiDictProxy[_T]]
+) -> int: ...
diff --git a/third_party/python/multidict/multidict/_abc.py b/third_party/python/multidict/multidict/_abc.py
new file mode 100644
index 0000000000..0603cdd244
--- /dev/null
+++ b/third_party/python/multidict/multidict/_abc.py
@@ -0,0 +1,48 @@
+import abc
+import sys
+import types
+from collections.abc import Mapping, MutableMapping
+
+
+class _TypingMeta(abc.ABCMeta):
+    # A fake metaclass to satisfy typing deps in runtime
+    # basically MultiMapping[str] and other generic-like type instantiations
+    # are emulated.
+    # Note: real type hints are provided by __init__.pyi stub file
+    if sys.version_info >= (3, 9):
+
+        def __getitem__(self, key):
+            return types.GenericAlias(self, key)
+
+    else:
+
+        def __getitem__(self, key):
+            return self
+
+
+class MultiMapping(Mapping, metaclass=_TypingMeta):
+    @abc.abstractmethod
+    def getall(self, key, default=None):
+        raise KeyError
+
+    @abc.abstractmethod
+    def getone(self, key, default=None):
+        raise KeyError
+
+
+class MutableMultiMapping(MultiMapping, MutableMapping):
+    @abc.abstractmethod
+    def add(self, key, value):
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def extend(self, *args, **kwargs):
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def popone(self, key, default=None):
+        raise KeyError
+
+    @abc.abstractmethod
+    def popall(self, key, default=None):
+        raise KeyError
diff --git a/third_party/python/multidict/multidict/_compat.py b/third_party/python/multidict/multidict/_compat.py
new file mode 100644
index 0000000000..e659124558
--- /dev/null
+++ b/third_party/python/multidict/multidict/_compat.py
@@ -0,0 +1,14 @@
+import os
+import platform
+
+NO_EXTENSIONS = bool(os.environ.get("MULTIDICT_NO_EXTENSIONS"))
+
+PYPY = platform.python_implementation() == "PyPy"
+
+USE_CYTHON_EXTENSIONS = USE_CYTHON = not NO_EXTENSIONS and not PYPY
+
+if USE_CYTHON_EXTENSIONS:
+    try:
+        from . import _multidict  # noqa
+    except ImportError:
+        USE_CYTHON_EXTENSIONS = USE_CYTHON = False
diff --git a/third_party/python/multidict/multidict/_multidict.c b/third_party/python/multidict/multidict/_multidict.c
new file mode 100644
index 0000000000..5bdcc898de
--- /dev/null
+++ b/third_party/python/multidict/multidict/_multidict.c
@@ -0,0 +1,1646 @@
+#include "Python.h"
+#include "structmember.h"
+
+// Include order important
+#include "_multilib/defs.h"
+#include "_multilib/istr.h"
+#include "_multilib/pair_list.h"
+#include "_multilib/dict.h"
+#include "_multilib/iter.h"
+#include "_multilib/views.h"
+
+static PyObject *collections_abc_mapping;
+static PyObject *collections_abc_mut_mapping;
+static PyObject *collections_abc_mut_multi_mapping;
+
+static PyTypeObject multidict_type;
+static PyTypeObject cimultidict_type;
+static PyTypeObject multidict_proxy_type;
+static PyTypeObject cimultidict_proxy_type;
+
+static PyObject *repr_func;
+
+#define MultiDict_CheckExact(o) (Py_TYPE(o) == &multidict_type)
+#define CIMultiDict_CheckExact(o) (Py_TYPE(o) == &cimultidict_type)
+#define MultiDictProxy_CheckExact(o) (Py_TYPE(o) == &multidict_proxy_type)
+#define CIMultiDictProxy_CheckExact(o) (Py_TYPE(o) == &cimultidict_proxy_type)
+
+/* Helper macro for something like isinstance(obj, Base) */
+#define _MultiDict_Check(o)              \
+    ((MultiDict_CheckExact(o)) ||        \
+     (CIMultiDict_CheckExact(o)) ||      \
+     (MultiDictProxy_CheckExact(o)) ||   \
+     (CIMultiDictProxy_CheckExact(o)))
+
+/******************** Internal Methods ********************/
+
+/* Forward declaration */
+static PyObject *multidict_items(MultiDictObject *self);
+
+static inline PyObject *
+_multidict_getone(MultiDictObject *self, PyObject *key, PyObject *_default)
+{
+    PyObject *val = pair_list_get_one(&self->pairs, key);
+
+    if (val == NULL &&
+        PyErr_ExceptionMatches(PyExc_KeyError) &&
+        _default != NULL)
+    {
+        PyErr_Clear();
+        Py_INCREF(_default);
+        return _default;
+    }
+
+    return val;
+}
+
+static inline int
+_multidict_eq(MultiDictObject *self, MultiDictObject *other)
+{
+    Py_ssize_t pos1 = 0,
+               pos2 = 0;
+
+    Py_hash_t h1 = 0,
+              h2 = 0;
+
+    PyObject *identity1 = NULL,
+             *identity2 = NULL,
+             *value1    = NULL,
+             *value2    = NULL;
+
+    int cmp_identity = 0,
+        cmp_value    = 0;
+
+    if (self == other) {
+        return 1;
+    }
+
+    if (pair_list_len(&self->pairs) != pair_list_len(&other->pairs)) {
+        return 0;
+    }
+
+    while (_pair_list_next(&self->pairs, &pos1, &identity1, NULL, &value1, &h1) &&
+           _pair_list_next(&other->pairs, &pos2, &identity2, NULL, &value2, &h2))
+    {
+        if (h1 != h2) {
+            return 0;
+        }
+        cmp_identity = PyObject_RichCompareBool(identity1, identity2, Py_NE);
+        if (cmp_identity < 0) {
+            return -1;
+        }
+        cmp_value = PyObject_RichCompareBool(value1, value2, Py_NE);
+        if (cmp_value < 0) {
+            return -1;
+        }
+        if (cmp_identity || cmp_value) {
+            return 0;
+        }
+    }
+
+    return 1;
+}
+
+static inline int
+_multidict_update_items(MultiDictObject *self, pair_list_t *pairs)
+{
+    return pair_list_update(&self->pairs, pairs);
+}
+
+static inline int
+_multidict_append_items(MultiDictObject *self, pair_list_t *pairs)
+{
+    PyObject *key   = NULL,
+             *value = NULL;
+
+    Py_ssize_t pos = 0;
+
+    while (_pair_list_next(pairs, &pos, NULL, &key, &value, NULL)) {
+        if (pair_list_add(&self->pairs, key, value) < 0) {
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
+static inline int
+_multidict_append_items_seq(MultiDictObject *self, PyObject *arg,
+                            const char *name)
+{
+    PyObject *key   = NULL,
+             *value = NULL,
+             *item  = NULL,
+             *iter  = PyObject_GetIter(arg);
+
+    if (iter == NULL) {
+        return -1;
+    }
+
+    while ((item = PyIter_Next(iter)) != NULL) {
+        if (PyTuple_CheckExact(item)) {
+            if (PyTuple_GET_SIZE(item) != 2) {
+                goto invalid_type;
+            }
+            key = PyTuple_GET_ITEM(item, 0);
+            Py_INCREF(key);
+            value = PyTuple_GET_ITEM(item, 1);
+            Py_INCREF(value);
+        }
+        else if (PyList_CheckExact(item)) {
+            if (PyList_GET_SIZE(item) != 2) {
+                goto invalid_type;
+            }
+            key = PyList_GET_ITEM(item, 0);
+            Py_INCREF(key);
+            value = PyList_GET_ITEM(item, 1);
+            Py_INCREF(value);
+        }
+        else if (PySequence_Check(item)) {
+            if (PySequence_Size(item) != 2) {
+                goto invalid_type;
+            }
+            key = PySequence_GetItem(item, 0);
+            value = PySequence_GetItem(item, 1);
+        } else {
+            goto invalid_type;
+        }
+
+        if (pair_list_add(&self->pairs, key, value) < 0) {
+            goto fail;
+        }
+        Py_CLEAR(key);
+        Py_CLEAR(value);
+        Py_CLEAR(item);
+    }
+
+    Py_DECREF(iter);
+
+    if (PyErr_Occurred()) {
+        return -1;
+    }
+
+    return 0;
+invalid_type:
+    PyErr_Format(
+        PyExc_TypeError,
+        "%s takes either dict or list of (key, value) pairs",
+        name,
+        NULL
+    );
+    goto fail;
+fail:
+    Py_XDECREF(key);
+    Py_XDECREF(value);
+    Py_XDECREF(item);
+    Py_DECREF(iter);
+    return -1;
+}
+
+static inline int
+_multidict_list_extend(PyObject *list, PyObject *target_list)
+{
+    PyObject *item = NULL,
+             *iter = PyObject_GetIter(target_list);
+
+    if (iter == NULL) {
+        return -1;
+    }
+
+    while ((item = PyIter_Next(iter)) != NULL) {
+        if (PyList_Append(list, item) < 0) {
+            Py_DECREF(item);
+            Py_DECREF(iter);
+            return -1;
+        }
+        Py_DECREF(item);
+    }
+
+    Py_DECREF(iter);
+
+    if (PyErr_Occurred()) {
+        return -1;
+    }
+
+    return 0;
+}
+
+static inline int
+_multidict_extend_with_args(MultiDictObject *self, PyObject *arg,
+                            PyObject *kwds, const char *name, int do_add)
+{
+    PyObject *arg_items  = NULL, /* tracked by GC */
+             *kwds_items = NULL; /* new reference */
+    pair_list_t *pairs = NULL;
+
+    int err = 0;
+
+    if (kwds && !PyArg_ValidateKeywordArguments(kwds)) {
+        return -1;
+    }
+
+    // TODO: mb can be refactored more clear
+    if (_MultiDict_Check(arg) && kwds == NULL) {
+        if (MultiDict_CheckExact(arg) || CIMultiDict_CheckExact(arg)) {
+            pairs = &((MultiDictObject*)arg)->pairs;
+        } else if (MultiDictProxy_CheckExact(arg) || CIMultiDictProxy_CheckExact(arg)) {
+            pairs = &((MultiDictProxyObject*)arg)->md->pairs;
+        }
+
+        if (do_add) {
+            return _multidict_append_items(self, pairs);
+        }
+
+        return _multidict_update_items(self, pairs);
+    }
+
+    if (PyObject_HasAttrString(arg, "items")) {
+        if (_MultiDict_Check(arg)) {
+            arg_items = multidict_items((MultiDictObject*)arg);
+        } else {
+            arg_items = PyMapping_Items(arg);
+        }
+        if (arg_items == NULL) {
+            return -1;
+        }
+    } else {
+        arg_items = arg;
+        Py_INCREF(arg_items);
+    }
+
+    if (kwds) {
+        PyObject *tmp = PySequence_List(arg_items);
+        Py_DECREF(arg_items);
+        arg_items = tmp;
+        if (arg_items == NULL) {
+            return -1;
+        }
+
+        kwds_items = PyDict_Items(kwds);
+        if (kwds_items == NULL) {
+            Py_DECREF(arg_items);
+            return -1;
+        }
+        err = _multidict_list_extend(arg_items, kwds_items);
+        Py_DECREF(kwds_items);
+        if (err < 0) {
+            Py_DECREF(arg_items);
+            return -1;
+        }
+    }
+
+    if (do_add) {
+        err = _multidict_append_items_seq(self, arg_items, name);
+    } else {
+        err =  pair_list_update_from_seq(&self->pairs, arg_items);
+    }
+
+    Py_DECREF(arg_items);
+
+    return err;
+}
+
+static inline int
+_multidict_extend_with_kwds(MultiDictObject *self, PyObject *kwds,
+                                 const char *name, int do_add)
+{
+    PyObject *arg = NULL;
+
+    int err = 0;
+
+    if (!PyArg_ValidateKeywordArguments(kwds)) {
+        return -1;
+    }
+
+    arg = PyDict_Items(kwds);
+    if (do_add) {
+        err = _multidict_append_items_seq(self, arg, name);
+    } else {
+        err = pair_list_update_from_seq(&self->pairs, arg);
+    }
+
+    Py_DECREF(arg);
+    return err;
+}
+
+static inline int
+_multidict_extend(MultiDictObject *self, PyObject *args, PyObject *kwds,
+                  const char *name, int do_add)
+{
+    PyObject *arg = NULL;
+
+    if (args && PyObject_Length(args) > 1)  {
+        PyErr_Format(
+            PyExc_TypeError,
+            "%s takes at most 1 positional argument (%zd given)",
+            name, PyObject_Length(args), NULL
+        );
+        return -1;
+    }
+
+    if (args && PyObject_Length(args) > 0) {
+        if (!PyArg_UnpackTuple(args, name, 0, 1, &arg)) {
+            return -1;
+        }
+        if (_multidict_extend_with_args(self, arg, kwds, name, do_add) < 0) {
+            return -1;
+        }
+    } else if (kwds && PyObject_Length(kwds) > 0) {
+        if (_multidict_extend_with_kwds(self, kwds, name, do_add) < 0) {
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
+static inline PyObject *
+_multidict_copy(MultiDictObject *self, PyTypeObject *multidict_tp_object)
+{
+    MultiDictObject *new_multidict = NULL;
+
+    PyObject *arg_items = NULL,
+             *items     = NULL;
+
+    new_multidict = (MultiDictObject*)PyType_GenericNew(
+        multidict_tp_object, NULL, NULL);
+    if (new_multidict == NULL) {
+        return NULL;
+    }
+
+    if (multidict_tp_object->tp_init(
+        (PyObject*)new_multidict, NULL, NULL) < 0)
+    {
+        return NULL;
+    }
+
+    items = multidict_items(self);
+    if (items == NULL) {
+        goto fail;
+    }
+
+    // TODO: "Implementation looks as slow as possible ..."
+    arg_items = PyTuple_New(1);
+    if (arg_items == NULL) {
+        goto fail;
+    }
+
+    Py_INCREF(items);
+    PyTuple_SET_ITEM(arg_items, 0, items);
+
+    if (_multidict_extend(
+        new_multidict, arg_items, NULL, "copy", 1) < 0)
+    {
+        goto fail;
+    }
+
+    Py_DECREF(items);
+    Py_DECREF(arg_items);
+
+    return (PyObject*)new_multidict;
+
+fail:
+    Py_XDECREF(items);
+    Py_XDECREF(arg_items);
+
+    Py_DECREF(new_multidict);
+
+    return NULL;
+}
+
+static inline PyObject *
+_multidict_proxy_copy(MultiDictProxyObject *self, PyTypeObject *type)
+{
+    PyObject *new_multidict = PyType_GenericNew(type, NULL, NULL);
+    if (new_multidict == NULL) {
+        goto fail;
+    }
+    if (type->tp_init(new_multidict, NULL, NULL) < 0) {
+        goto fail;
+    }
+    if (_multidict_extend_with_args(
+        (MultiDictObject*)new_multidict, (PyObject*)self, NULL, "copy", 1) < 0)
+    {
+        goto fail;
+    }
+
+    return new_multidict;
+
+fail:
+    Py_XDECREF(new_multidict);
+    return NULL;
+}
+
+
+/******************** Base Methods ********************/
+
+static inline PyObject *
+multidict_getall(MultiDictObject *self, PyObject *args, PyObject *kwds)
+{
+    PyObject *list     = NULL,
+             *key      = NULL,
+             *_default = NULL;
+
+    static char *getall_keywords[] = {"key", "default", NULL};
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|O:getall",
+                                     getall_keywords, &key, &_default))
+    {
+        return NULL;
+    }
+
+    list = pair_list_get_all(&self->pairs, key);
+
+    if (list == NULL &&
+        PyErr_ExceptionMatches(PyExc_KeyError) &&
+        _default != NULL)
+    {
+        PyErr_Clear();
+        Py_INCREF(_default);
+        return _default;
+    }
+
+    return list;
+}
+
+static inline PyObject *
+multidict_getone(MultiDictObject *self, PyObject *args, PyObject *kwds)
+{
+    PyObject *key      = NULL,
+             *_default = NULL;
+
+    static char *getone_keywords[] = {"key", "default", NULL};
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|O:getone",
+                                     getone_keywords, &key, &_default))
+    {
+        return NULL;
+    }
+
+    return _multidict_getone(self, key, _default);
+}
+
+static inline PyObject *
+multidict_get(MultiDictObject *self, PyObject *args, PyObject *kwds)
+{
+    PyObject *key      = NULL,
+             *_default = Py_None,
+             *ret;
+
+    static char *getone_keywords[] = {"key", "default", NULL};
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|O:getone",
+                                     getone_keywords, &key, &_default))
+    {
+        return NULL;
+    }
+    ret = _multidict_getone(self, key, _default);
+    return ret;
+}
+
+static inline PyObject *
+multidict_keys(MultiDictObject *self)
+{
+    return multidict_keysview_new((PyObject*)self);
+}
+
+static inline PyObject *
+multidict_items(MultiDictObject *self)
+{
+    return multidict_itemsview_new((PyObject*)self);
+}
+
+static inline PyObject *
+multidict_values(MultiDictObject *self)
+{
+    return multidict_valuesview_new((PyObject*)self);
+}
+
+static inline PyObject *
+multidict_reduce(MultiDictObject *self)
+{
+    PyObject *items      = NULL,
+             *items_list = NULL,
+             *args       = NULL,
+             *result     = NULL;
+
+    items = multidict_items(self);
+    if (items == NULL) {
+        goto ret;
+    }
+
+    items_list = PySequence_List(items);
+    if (items_list == NULL) {
+        goto ret;
+    }
+
+    args = PyTuple_Pack(1, items_list);
+    if (args == NULL) {
+        goto ret;
+    }
+
+    result = PyTuple_Pack(2, Py_TYPE(self), args);
+
+ret:
+    Py_XDECREF(args);
+    Py_XDECREF(items_list);
+    Py_XDECREF(items);
+
+    return result;
+}
+
+static inline PyObject *
+multidict_repr(PyObject *self)
+{
+    return PyObject_CallFunctionObjArgs(
+        repr_func, self, NULL);
+}
+
+static inline Py_ssize_t
+multidict_mp_len(MultiDictObject *self)
+{
+    return pair_list_len(&self->pairs);
+}
+
+static inline PyObject *
+multidict_mp_subscript(MultiDictObject *self, PyObject *key)
+{
+    return _multidict_getone(self, key, NULL);
+}
+
+static inline int
+multidict_mp_as_subscript(MultiDictObject *self, PyObject *key, PyObject *val)
+{
+    if (val == NULL) {
+        return pair_list_del(&self->pairs, key);
+    } else {
+        return pair_list_replace(&self->pairs, key, val);
+    }
+}
+
+static inline int
+multidict_sq_contains(MultiDictObject *self, PyObject *key)
+{
+    return pair_list_contains(&self->pairs, key);
+}
+
+static inline PyObject *
+multidict_tp_iter(MultiDictObject *self)
+{
+    return multidict_keys_iter_new(self);
+}
+
+static inline PyObject *
+multidict_tp_richcompare(PyObject *self, PyObject *other, int op)
+{
+    // TODO: refactoring me with love
+
+    int cmp = 0;
+
+    if (op != Py_EQ && op != Py_NE) {
+        Py_RETURN_NOTIMPLEMENTED;
+    }
+
+    if (MultiDict_CheckExact(other) || CIMultiDict_CheckExact(other)) {
+        cmp = _multidict_eq(
+            (MultiDictObject*)self,
+            (MultiDictObject*)other
+        );
+        if (cmp < 0) {
+            return NULL;
+        }
+        if (op == Py_NE) {
+            cmp = !cmp;
+        }
+        return PyBool_FromLong(cmp);
+    }
+
+    if (MultiDictProxy_CheckExact(other) || CIMultiDictProxy_CheckExact(other)) {
+        cmp = _multidict_eq(
+            (MultiDictObject*)self,
+            ((MultiDictProxyObject*)other)->md
+        );
+        if (cmp < 0) {
+            return NULL;
+        }
+        if (op == Py_NE) {
+            cmp = !cmp;
+        }
+        return PyBool_FromLong(cmp);
+    }
+
+    cmp = PyObject_IsInstance(other, (PyObject*)collections_abc_mapping);
+    if (cmp < 0) {
+        return NULL;
+    }
+
+    if (cmp) {
+        cmp = pair_list_eq_to_mapping(&((MultiDictObject*)self)->pairs, other);
+        if (cmp < 0) {
+            return NULL;
+        }
+        if (op == Py_NE) {
+            cmp = !cmp;
+        }
+        return PyBool_FromLong(cmp);
+    }
+
+    Py_RETURN_NOTIMPLEMENTED;
+}
+
+static inline void
+multidict_tp_dealloc(MultiDictObject *self)
+{
+    PyObject_GC_UnTrack(self);
+    Py_TRASHCAN_SAFE_BEGIN(self);
+    if (self->weaklist != NULL) {
+        PyObject_ClearWeakRefs((PyObject *)self);
+    };
+    pair_list_dealloc(&self->pairs);
+    Py_TYPE(self)->tp_free((PyObject *)self);
+    Py_TRASHCAN_SAFE_END(self);
+}
+
+static inline int
+multidict_tp_traverse(MultiDictObject *self, visitproc visit, void *arg)
+{
+    return pair_list_traverse(&self->pairs, visit, arg);
+}
+
+static inline int
+multidict_tp_clear(MultiDictObject *self)
+{
+    return pair_list_clear(&self->pairs);
+}
+
+PyDoc_STRVAR(multidict_getall_doc,
+"Return a list of all values matching the key.");
+
+PyDoc_STRVAR(multidict_getone_doc,
+"Get first value matching the key.");
+
+PyDoc_STRVAR(multidict_get_doc,
+"Get first value matching the key.\n\nThe method is alias for .getone().");
+
+PyDoc_STRVAR(multidict_keys_doc,
+"Return a new view of the dictionary's keys.");
+
+PyDoc_STRVAR(multidict_items_doc,
+"Return a new view of the dictionary's items *(key, value) pairs).");
+
+PyDoc_STRVAR(multidict_values_doc,
+"Return a new view of the dictionary's values.");
+
+/******************** MultiDict ********************/
+
+static inline int
+multidict_tp_init(MultiDictObject *self, PyObject *args, PyObject *kwds)
+{
+    if (pair_list_init(&self->pairs) < 0) {
+        return -1;
+    }
+    if (_multidict_extend(self, args, kwds, "MultiDict", 1) < 0) {
+        return -1;
+    }
+    return 0;
+}
+
+static inline PyObject *
+multidict_add(MultiDictObject *self, PyObject *args, PyObject *kwds)
+{
+    PyObject *key = NULL,
+             *val = NULL;
+
+    static char *kwlist[] = {"key", "value", NULL};
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "OO:add",
+                                     kwlist, &key, &val))
+    {
+        return NULL;
+    }
+
+    if (pair_list_add(&self->pairs, key, val) < 0) {
+        return NULL;
+    }
+
+    Py_RETURN_NONE;
+}
+
+static inline PyObject *
+multidict_copy(MultiDictObject *self)
+{
+    return _multidict_copy(self, &multidict_type);
+}
+
+static inline PyObject *
+multidict_extend(MultiDictObject *self, PyObject *args, PyObject *kwds)
+{
+    if (_multidict_extend(self, args, kwds, "extend", 1) < 0) {
+        return NULL;
+    }
+
+    Py_RETURN_NONE;
+}
+
+static inline PyObject *
+multidict_clear(MultiDictObject *self)
+{
+    if (pair_list_clear(&self->pairs) < 0) {
+        return NULL;
+    }
+
+    Py_RETURN_NONE;
+}
+
+static inline PyObject *
+multidict_setdefault(MultiDictObject *self, PyObject *args, PyObject *kwds)
+{
+    PyObject *key      = NULL,
+             *_default = NULL;
+
+    static char *setdefault_keywords[] = {"key", "default", NULL};
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|O:setdefault",
+                                     setdefault_keywords, &key, &_default))
+    {
+        return NULL;
+    }
+    return pair_list_set_default(&self->pairs, key, _default);
+}
+
+static inline PyObject *
+multidict_popone(MultiDictObject *self, PyObject *args, PyObject *kwds)
+{
+    PyObject *key      = NULL,
+             *_default = NULL,
+             *ret_val  = NULL;
+
+    static char *popone_keywords[] = {"key", "default", NULL};
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|O:popone",
+                                     popone_keywords, &key, &_default))
+    {
+        return NULL;
+    }
+
+    ret_val = pair_list_pop_one(&self->pairs, key);
+
+    if (ret_val == NULL &&
+        PyErr_ExceptionMatches(PyExc_KeyError) &&
+        _default != NULL)
+    {
+        PyErr_Clear();
+        Py_INCREF(_default);
+        return _default;
+    }
+
+    return ret_val;
+}
+
+static inline PyObject *
+multidict_popall(MultiDictObject *self, PyObject *args, PyObject *kwds)
+{
+    PyObject *key      = NULL,
+             *_default = NULL,
+             *ret_val  = NULL;
+
+    static char *popall_keywords[] = {"key", "default", NULL};
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|O:popall",
+                                     popall_keywords, &key, &_default))
+    {
+        return NULL;
+    }
+
+    ret_val = pair_list_pop_all(&self->pairs, key);
+
+    if (ret_val == NULL &&
+        PyErr_ExceptionMatches(PyExc_KeyError) &&
+        _default != NULL)
+    {
+        PyErr_Clear();
+        Py_INCREF(_default);
+        return _default;
+    }
+
+    return ret_val;
+}
+
+static inline PyObject *
+multidict_popitem(MultiDictObject *self)
+{
+    return pair_list_pop_item(&self->pairs);
+}
+
+static inline PyObject *
+multidict_update(MultiDictObject *self, PyObject *args, PyObject *kwds)
+{
+    if (_multidict_extend(self, args, kwds, "update", 0) < 0) {
+        return NULL;
+    }
+    Py_RETURN_NONE;
+}
+
+PyDoc_STRVAR(multidict_add_doc,
+"Add the key and value, not overwriting any previous value.");
+
+PyDoc_STRVAR(multidict_copy_doc,
+"Return a copy of itself.");
+
+PyDoc_STRVAR(multdicit_method_extend_doc,
+"Extend current MultiDict with more values.\n\
+This method must be used instead of update.");
+
+PyDoc_STRVAR(multidict_clear_doc,
+"Remove all items from MultiDict");
+
+PyDoc_STRVAR(multidict_setdefault_doc,
+"Return value for key, set value to default if key is not present.");
+
+PyDoc_STRVAR(multidict_popone_doc,
+"Remove the last occurrence of key and return the corresponding value.\n\n\
+If key is not found, default is returned if given, otherwise KeyError is \
+raised.\n");
+
+PyDoc_STRVAR(multidict_popall_doc,
+"Remove all occurrences of key and return the list of corresponding values.\n\n\
+If key is not found, default is returned if given, otherwise KeyError is \
+raised.\n");
+
+PyDoc_STRVAR(multidict_popitem_doc,
+"Remove and return an arbitrary (key, value) pair.");
+
+PyDoc_STRVAR(multidict_update_doc,
+"Update the dictionary from *other*, overwriting existing keys.");
+
+
+#if PY_MAJOR_VERSION >= 3 && PY_MINOR_VERSION >= 9
+#define multidict_class_getitem Py_GenericAlias
+#else
+static inline PyObject *
+multidict_class_getitem(PyObject *self, PyObject *arg)
+{
+    Py_INCREF(self);
+    return self;
+}
+#endif
+
+
+PyDoc_STRVAR(sizeof__doc__,
+"D.__sizeof__() -> size of D in memory, in bytes");
+
+static inline PyObject *
+_multidict_sizeof(MultiDictObject *self)
+{
+    Py_ssize_t size = sizeof(MultiDictObject);
+    if (self->pairs.pairs != self->pairs.buffer) {
+        size += (Py_ssize_t)sizeof(pair_t) * self->pairs.capacity;
+    }
+    return PyLong_FromSsize_t(size);
+}
+
+
+static PySequenceMethods multidict_sequence = {
+    .sq_contains = (objobjproc)multidict_sq_contains,
+};
+
+static PyMappingMethods multidict_mapping = {
+    .mp_length = (lenfunc)multidict_mp_len,
+    .mp_subscript = (binaryfunc)multidict_mp_subscript,
+    .mp_ass_subscript = (objobjargproc)multidict_mp_as_subscript,
+};
+
+static PyMethodDef multidict_methods[] = {
+    {
+        "getall",
+        (PyCFunction)multidict_getall,
+        METH_VARARGS | METH_KEYWORDS,
+        multidict_getall_doc
+    },
+    {
+        "getone",
+        (PyCFunction)multidict_getone,
+        METH_VARARGS | METH_KEYWORDS,
+        multidict_getone_doc
+    },
+    {
+        "get",
+        (PyCFunction)multidict_get,
+        METH_VARARGS | METH_KEYWORDS,
+        multidict_get_doc
+    },
+    {
+        "keys",
+        (PyCFunction)multidict_keys,
+        METH_NOARGS,
+        multidict_keys_doc
+    },
+    {
+        "items",
+        (PyCFunction)multidict_items,
+        METH_NOARGS,
+        multidict_items_doc
+    },
+    {
+        "values",
+        (PyCFunction)multidict_values,
+        METH_NOARGS,
+        multidict_values_doc
+    },
+    {
+        "add",
+        (PyCFunction)multidict_add,
+        METH_VARARGS | METH_KEYWORDS,
+        multidict_add_doc
+    },
+    {
+        "copy",
+        (PyCFunction)multidict_copy,
+        METH_NOARGS,
+        multidict_copy_doc
+    },
+    {
+        "extend",
+        (PyCFunction)multidict_extend,
+        METH_VARARGS | METH_KEYWORDS,
+        multdicit_method_extend_doc
+    },
+    {
+        "clear",
+        (PyCFunction)multidict_clear,
+        METH_NOARGS,
+        multidict_clear_doc
+    },
+    {
+        "setdefault",
+        (PyCFunction)multidict_setdefault,
+        METH_VARARGS | METH_KEYWORDS,
+        multidict_setdefault_doc
+    },
+    {
+        "popone",
+        (PyCFunction)multidict_popone,
+        METH_VARARGS | METH_KEYWORDS,
+        multidict_popone_doc
+    },
+    {
+        "pop",
+        (PyCFunction)multidict_popone,
+        METH_VARARGS | METH_KEYWORDS,
+        multidict_popone_doc
+    },
+    {
+        "popall",
+        (PyCFunction)multidict_popall,
+        METH_VARARGS | METH_KEYWORDS,
+        multidict_popall_doc
+    },
+    {
+        "popitem",
+        (PyCFunction)multidict_popitem,
+        METH_NOARGS,
+        multidict_popitem_doc
+    },
+    {
+        "update",
+        (PyCFunction)multidict_update,
+        METH_VARARGS | METH_KEYWORDS,
+        multidict_update_doc
+    },
+    {
+        "__reduce__",
+        (PyCFunction)multidict_reduce,
+        METH_NOARGS,
+        NULL,
+    },
+    {
+        "__class_getitem__",
+        (PyCFunction)multidict_class_getitem,
+        METH_O | METH_CLASS,
+        NULL
+    },
+    {
+        "__sizeof__",
+        (PyCFunction)_multidict_sizeof,
+        METH_NOARGS,
+        sizeof__doc__,
+    },
+    {
+        NULL,
+        NULL
+    }   /* sentinel */
+};
+
+
+PyDoc_STRVAR(MultDict_doc,
+"Dictionary with the support for duplicate keys.");
+
+
+static PyTypeObject multidict_type = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    "multidict._multidict.MultiDict",                /* tp_name */
+    sizeof(MultiDictObject),                         /* tp_basicsize */
+    .tp_dealloc = (destructor)multidict_tp_dealloc,
+    .tp_repr = (reprfunc)multidict_repr,
+    .tp_as_sequence = &multidict_sequence,
+    .tp_as_mapping = &multidict_mapping,
+    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
+    .tp_doc = MultDict_doc,
+    .tp_traverse = (traverseproc)multidict_tp_traverse,
+    .tp_clear = (inquiry)multidict_tp_clear,
+    .tp_richcompare = (richcmpfunc)multidict_tp_richcompare,
+    .tp_weaklistoffset = offsetof(MultiDictObject, weaklist),
+    .tp_iter = (getiterfunc)multidict_tp_iter,
+    .tp_methods = multidict_methods,
+    .tp_init = (initproc)multidict_tp_init,
+    .tp_alloc = PyType_GenericAlloc,
+    .tp_new = PyType_GenericNew,
+    .tp_free = PyObject_GC_Del,
+};
+
+/******************** CIMultiDict ********************/
+
+static inline int
+cimultidict_tp_init(MultiDictObject *self, PyObject *args, PyObject *kwds)
+{
+    if (ci_pair_list_init(&self->pairs) < 0) {
+        return -1;
+    }
+    if (_multidict_extend(self, args, kwds, "CIMultiDict", 1) < 0) {
+        return -1;
+    }
+    return 0;
+}
+
+static inline PyObject *
+cimultidict_copy(MultiDictObject *self)
+{
+    return _multidict_copy(self, &cimultidict_type);
+}
+
+PyDoc_STRVAR(cimultidict_copy_doc,
+"Return a copy of itself.");
+
+static PyMethodDef cimultidict_methods[] = {
+    {
+        "copy",
+        (PyCFunction)cimultidict_copy,
+        METH_NOARGS,
+        cimultidict_copy_doc
+    },
+    {
+        NULL,
+        NULL
+    }   /* sentinel */
+};
+
+PyDoc_STRVAR(CIMultDict_doc,
+"Dictionary with the support for duplicate case-insensitive keys.");
+
+
+static PyTypeObject cimultidict_type = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    "multidict._multidict.CIMultiDict",              /* tp_name */
+    sizeof(MultiDictObject),                         /* tp_basicsize */
+    .tp_dealloc = (destructor)multidict_tp_dealloc,
+    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
+    .tp_doc = CIMultDict_doc,
+    .tp_traverse = (traverseproc)multidict_tp_traverse,
+    .tp_clear = (inquiry)multidict_tp_clear,
+    .tp_weaklistoffset = offsetof(MultiDictObject, weaklist),
+    .tp_methods = cimultidict_methods,
+    .tp_base = &multidict_type,
+    .tp_init = (initproc)cimultidict_tp_init,
+    .tp_alloc = PyType_GenericAlloc,
+    .tp_new = PyType_GenericNew,
+    .tp_free = PyObject_GC_Del,
+};
+
+/******************** MultiDictProxy ********************/
+
+static inline int
+multidict_proxy_tp_init(MultiDictProxyObject *self, PyObject *args,
+                        PyObject *kwds)
+{
+    PyObject        *arg = NULL;
+    MultiDictObject *md  = NULL;
+
+    if (!PyArg_UnpackTuple(args, "multidict._multidict.MultiDictProxy",
+                           0, 1, &arg))
+    {
+        return -1;
+    }
+    if (arg == NULL) {
+        PyErr_Format(
+            PyExc_TypeError,
+            "__init__() missing 1 required positional argument: 'arg'"
+        );
+        return -1;
+    }
+    if (!MultiDictProxy_CheckExact(arg) &&
+        !CIMultiDict_CheckExact(arg) &&
+        !MultiDict_CheckExact(arg))
+    {
+        PyErr_Format(
+            PyExc_TypeError,
+            "ctor requires MultiDict or MultiDictProxy instance, "
+            "not <classs '%s'>",
+            Py_TYPE(arg)->tp_name
+        );
+        return -1;
+    }
+
+    md = (MultiDictObject*)arg;
+    if (MultiDictProxy_CheckExact(arg)) {
+        md = ((MultiDictProxyObject*)arg)->md;
+    }
+    Py_INCREF(md);
+    self->md = md;
+
+    return 0;
+}
+
+static inline PyObject *
+multidict_proxy_getall(MultiDictProxyObject *self, PyObject *args,
+                       PyObject *kwds)
+{
+    return multidict_getall(self->md, args, kwds);
+}
+
+static inline PyObject *
+multidict_proxy_getone(MultiDictProxyObject *self, PyObject *args,
+                       PyObject *kwds)
+{
+    return multidict_getone(self->md, args, kwds);
+}
+
+static inline PyObject *
+multidict_proxy_get(MultiDictProxyObject *self, PyObject *args,
+                       PyObject *kwds)
+{
+    return multidict_get(self->md, args, kwds);
+}
+
+static inline PyObject *
+multidict_proxy_keys(MultiDictProxyObject *self)
+{
+    return multidict_keys(self->md);
+}
+
+static inline PyObject *
+multidict_proxy_items(MultiDictProxyObject *self)
+{
+    return multidict_items(self->md);
+}
+
+static inline PyObject *
+multidict_proxy_values(MultiDictProxyObject *self)
+{
+    return multidict_values(self->md);
+}
+
+static inline PyObject *
+multidict_proxy_copy(MultiDictProxyObject *self)
+{
+    return _multidict_proxy_copy(self, &multidict_type);
+}
+
+static inline PyObject *
+multidict_proxy_reduce(MultiDictProxyObject *self)
+{
+    PyErr_Format(
+        PyExc_TypeError,
+        "can't pickle %s objects", Py_TYPE(self)->tp_name
+    );
+
+    return NULL;
+}
+
+static inline Py_ssize_t
+multidict_proxy_mp_len(MultiDictProxyObject *self)
+{
+    return multidict_mp_len(self->md);
+}
+
+static inline PyObject *
+multidict_proxy_mp_subscript(MultiDictProxyObject *self, PyObject *key)
+{
+    return multidict_mp_subscript(self->md, key);
+}
+
+static inline int
+multidict_proxy_sq_contains(MultiDictProxyObject *self, PyObject *key)
+{
+    return multidict_sq_contains(self->md, key);
+}
+
+static inline PyObject *
+multidict_proxy_tp_iter(MultiDictProxyObject *self)
+{
+    return multidict_tp_iter(self->md);
+}
+
+static inline PyObject *
+multidict_proxy_tp_richcompare(MultiDictProxyObject *self, PyObject *other,
+                               int op)
+{
+    return multidict_tp_richcompare((PyObject*)self->md, other, op);
+}
+
+static inline void
+multidict_proxy_tp_dealloc(MultiDictProxyObject *self)
+{
+    PyObject_GC_UnTrack(self);
+    if (self->weaklist != NULL) {
+        PyObject_ClearWeakRefs((PyObject *)self);
+    };
+    Py_XDECREF(self->md);
+    Py_TYPE(self)->tp_free((PyObject *)self);
+}
+
+static inline int
+multidict_proxy_tp_traverse(MultiDictProxyObject *self, visitproc visit,
+                            void *arg)
+{
+    Py_VISIT(self->md);
+    return 0;
+}
+
+static inline int
+multidict_proxy_tp_clear(MultiDictProxyObject *self)
+{
+    Py_CLEAR(self->md);
+    return 0;
+}
+
+static PySequenceMethods multidict_proxy_sequence = {
+    .sq_contains = (objobjproc)multidict_proxy_sq_contains,
+};
+
+static PyMappingMethods multidict_proxy_mapping = {
+    .mp_length = (lenfunc)multidict_proxy_mp_len,
+    .mp_subscript = (binaryfunc)multidict_proxy_mp_subscript,
+};
+
+static PyMethodDef multidict_proxy_methods[] = {
+    {
+        "getall",
+        (PyCFunction)multidict_proxy_getall,
+        METH_VARARGS | METH_KEYWORDS,
+        multidict_getall_doc
+    },
+    {
+        "getone",
+        (PyCFunction)multidict_proxy_getone,
+        METH_VARARGS | METH_KEYWORDS,
+        multidict_getone_doc
+    },
+    {
+        "get",
+        (PyCFunction)multidict_proxy_get,
+        METH_VARARGS | METH_KEYWORDS,
+        multidict_get_doc
+    },
+    {
+        "keys",
+        (PyCFunction)multidict_proxy_keys,
+        METH_NOARGS,
+        multidict_keys_doc
+    },
+    {
+        "items",
+        (PyCFunction)multidict_proxy_items,
+        METH_NOARGS,
+        multidict_items_doc
+    },
+    {
+        "values",
+        (PyCFunction)multidict_proxy_values,
+        METH_NOARGS,
+        multidict_values_doc
+    },
+    {
+        "copy",
+        (PyCFunction)multidict_proxy_copy,
+        METH_NOARGS,
+        multidict_copy_doc
+    },
+    {
+        "__reduce__",
+        (PyCFunction)multidict_proxy_reduce,
+        METH_NOARGS,
+        NULL
+    },
+    {
+        "__class_getitem__",
+        (PyCFunction)multidict_class_getitem,
+        METH_O | METH_CLASS,
+        NULL
+    },
+    {
+        NULL,
+        NULL
+    }   /* sentinel */
+};
+
+
+PyDoc_STRVAR(MultDictProxy_doc,
+"Read-only proxy for MultiDict instance.");
+
+
+static PyTypeObject multidict_proxy_type = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    "multidict._multidict.MultiDictProxy",           /* tp_name */
+    sizeof(MultiDictProxyObject),                    /* tp_basicsize */
+    .tp_dealloc = (destructor)multidict_proxy_tp_dealloc,
+    .tp_repr = (reprfunc)multidict_repr,
+    .tp_as_sequence = &multidict_proxy_sequence,
+    .tp_as_mapping = &multidict_proxy_mapping,
+    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
+    .tp_doc = MultDictProxy_doc,
+    .tp_traverse = (traverseproc)multidict_proxy_tp_traverse,
+    .tp_clear = (inquiry)multidict_proxy_tp_clear,
+    .tp_richcompare = (richcmpfunc)multidict_proxy_tp_richcompare,
+    .tp_weaklistoffset = offsetof(MultiDictProxyObject, weaklist),
+    .tp_iter = (getiterfunc)multidict_proxy_tp_iter,
+    .tp_methods = multidict_proxy_methods,
+    .tp_init = (initproc)multidict_proxy_tp_init,
+    .tp_alloc = PyType_GenericAlloc,
+    .tp_new = PyType_GenericNew,
+    .tp_free = PyObject_GC_Del,
+};
+
+/******************** CIMultiDictProxy ********************/
+
+static inline int
+cimultidict_proxy_tp_init(MultiDictProxyObject *self, PyObject *args,
+                          PyObject *kwds)
+{
+    PyObject        *arg = NULL;
+    MultiDictObject *md  = NULL;
+
+    if (!PyArg_UnpackTuple(args, "multidict._multidict.CIMultiDictProxy",
+                           1, 1, &arg))
+    {
+        return -1;
+    }
+    if (arg == NULL) {
+        PyErr_Format(
+            PyExc_TypeError,
+            "__init__() missing 1 required positional argument: 'arg'"
+        );
+        return -1;
+    }
+    if (!CIMultiDictProxy_CheckExact(arg) && !CIMultiDict_CheckExact(arg)) {
+        PyErr_Format(
+            PyExc_TypeError,
+            "ctor requires CIMultiDict or CIMultiDictProxy instance, "
+            "not <class '%s'>",
+            Py_TYPE(arg)->tp_name
+        );
+        return -1;
+    }
+
+    md = (MultiDictObject*)arg;
+    if (CIMultiDictProxy_CheckExact(arg)) {
+        md = ((MultiDictProxyObject*)arg)->md;
+    }
+    Py_INCREF(md);
+    self->md = md;
+
+    return 0;
+}
+
+static inline PyObject *
+cimultidict_proxy_copy(MultiDictProxyObject *self)
+{
+    return _multidict_proxy_copy(self, &cimultidict_type);
+}
+
+
+PyDoc_STRVAR(CIMultDictProxy_doc,
+"Read-only proxy for CIMultiDict instance.");
+
+PyDoc_STRVAR(cimultidict_proxy_copy_doc,
+"Return copy of itself");
+
+static PyMethodDef cimultidict_proxy_methods[] = {
+    {
+        "copy",
+        (PyCFunction)cimultidict_proxy_copy,
+        METH_NOARGS,
+        cimultidict_proxy_copy_doc
+    },
+    {
+        NULL,
+        NULL
+    }   /* sentinel */
+};
+
+static PyTypeObject cimultidict_proxy_type = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    "multidict._multidict.CIMultiDictProxy",         /* tp_name */
+    sizeof(MultiDictProxyObject),                    /* tp_basicsize */
+    .tp_dealloc = (destructor)multidict_proxy_tp_dealloc,
+    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
+    .tp_doc = CIMultDictProxy_doc,
+    .tp_traverse = (traverseproc)multidict_proxy_tp_traverse,
+    .tp_clear = (inquiry)multidict_proxy_tp_clear,
+    .tp_richcompare = (richcmpfunc)multidict_proxy_tp_richcompare,
+    .tp_weaklistoffset = offsetof(MultiDictProxyObject, weaklist),
+    .tp_methods = cimultidict_proxy_methods,
+    .tp_base = &multidict_proxy_type,
+    .tp_init = (initproc)cimultidict_proxy_tp_init,
+    .tp_alloc = PyType_GenericAlloc,
+    .tp_new = PyType_GenericNew,
+    .tp_free = PyObject_GC_Del,
+};
+
+/******************** Other functions ********************/
+
+static inline PyObject *
+getversion(PyObject *self, PyObject *md)
+{
+    pair_list_t *pairs = NULL;
+    if (MultiDict_CheckExact(md) || CIMultiDict_CheckExact(md)) {
+        pairs = &((MultiDictObject*)md)->pairs;
+    } else if (MultiDictProxy_CheckExact(md) || CIMultiDictProxy_CheckExact(md)) {
+        pairs = &((MultiDictProxyObject*)md)->md->pairs;
+    } else {
+        PyErr_Format(PyExc_TypeError, "unexpected type");
+        return NULL;
+    }
+    return PyLong_FromUnsignedLong(pair_list_version(pairs));
+}
+
+/******************** Module ********************/
+
+static inline void
+module_free(void *m)
+{
+    Py_CLEAR(collections_abc_mapping);
+    Py_CLEAR(collections_abc_mut_mapping);
+    Py_CLEAR(collections_abc_mut_multi_mapping);
+}
+
+static PyMethodDef multidict_module_methods[] = {
+    {
+        "getversion",
+        (PyCFunction)getversion,
+        METH_O
+    },
+    {
+        NULL,
+        NULL
+    }   /* sentinel */
+};
+
+static PyModuleDef multidict_module = {
+    PyModuleDef_HEAD_INIT,      /* m_base */
+    "_multidict",               /* m_name */
+    .m_size = -1,
+    .m_methods = multidict_module_methods,
+    .m_free = (freefunc)module_free,
+};
+
+PyMODINIT_FUNC
+PyInit__multidict()
+{
+    PyObject *module = NULL,
+             *reg_func_call_result = NULL;
+
+#define WITH_MOD(NAME)                      \
+    Py_CLEAR(module);                       \
+    module = PyImport_ImportModule(NAME);   \
+    if (module == NULL) {                   \
+        goto fail;                          \
+    }
+
+#define GET_MOD_ATTR(VAR, NAME)                 \
+    VAR = PyObject_GetAttrString(module, NAME); \
+    if (VAR == NULL) {                          \
+        goto fail;                              \
+    }
+
+    if (multidict_views_init() < 0) {
+        goto fail;
+    }
+
+    if (multidict_iter_init() < 0) {
+        goto fail;
+    }
+
+    if (istr_init() < 0) {
+        goto fail;
+    }
+
+    if (PyType_Ready(&multidict_type) < 0 ||
+        PyType_Ready(&cimultidict_type) < 0 ||
+        PyType_Ready(&multidict_proxy_type) < 0 ||
+        PyType_Ready(&cimultidict_proxy_type) < 0)
+    {
+        goto fail;
+    }
+
+    WITH_MOD("collections.abc");
+    GET_MOD_ATTR(collections_abc_mapping, "Mapping");
+
+    WITH_MOD("multidict._abc");
+    GET_MOD_ATTR(collections_abc_mut_mapping, "MultiMapping");
+
+    WITH_MOD("multidict._abc");
+    GET_MOD_ATTR(collections_abc_mut_multi_mapping, "MutableMultiMapping");
+
+    WITH_MOD("multidict._multidict_base");
+    GET_MOD_ATTR(repr_func, "_mdrepr");
+
+    /* Register in _abc mappings (CI)MultiDict and (CI)MultiDictProxy */
+    reg_func_call_result = PyObject_CallMethod(
+        collections_abc_mut_mapping,
+        "register", "O",
+        (PyObject*)&multidict_proxy_type
+    );
+    if (reg_func_call_result == NULL) {
+        goto fail;
+    }
+    Py_DECREF(reg_func_call_result);
+
+    reg_func_call_result = PyObject_CallMethod(
+        collections_abc_mut_mapping,
+        "register", "O",
+        (PyObject*)&cimultidict_proxy_type
+    );
+    if (reg_func_call_result == NULL) {
+        goto fail;
+    }
+    Py_DECREF(reg_func_call_result);
+
+    reg_func_call_result = PyObject_CallMethod(
+        collections_abc_mut_multi_mapping,
+        "register", "O",
+        (PyObject*)&multidict_type
+    );
+    if (reg_func_call_result == NULL) {
+        goto fail;
+    }
+    Py_DECREF(reg_func_call_result);
+
+    reg_func_call_result = PyObject_CallMethod(
+        collections_abc_mut_multi_mapping,
+        "register", "O",
+        (PyObject*)&cimultidict_type
+    );
+    if (reg_func_call_result == NULL) {
+        goto fail;
+    }
+    Py_DECREF(reg_func_call_result);
+
+    /* Instantiate this module */
+    module = PyModule_Create(&multidict_module);
+
+    Py_INCREF(&istr_type);
+    if (PyModule_AddObject(
+            module, "istr", (PyObject*)&istr_type) < 0)
+    {
+        goto fail;
+    }
+
+    Py_INCREF(&multidict_type);
+    if (PyModule_AddObject(
+            module, "MultiDict", (PyObject*)&multidict_type) < 0)
+    {
+        goto fail;
+    }
+
+    Py_INCREF(&cimultidict_type);
+    if (PyModule_AddObject(
+            module, "CIMultiDict", (PyObject*)&cimultidict_type) < 0)
+    {
+        goto fail;
+    }
+
+    Py_INCREF(&multidict_proxy_type);
+    if (PyModule_AddObject(
+            module, "MultiDictProxy", (PyObject*)&multidict_proxy_type) < 0)
+    {
+        goto fail;
+    }
+
+    Py_INCREF(&cimultidict_proxy_type);
+    if (PyModule_AddObject(
+            module, "CIMultiDictProxy", (PyObject*)&cimultidict_proxy_type) < 0)
+    {
+        goto fail;
+    }
+
+    return module;
+
+fail:
+    Py_XDECREF(collections_abc_mapping);
+    Py_XDECREF(collections_abc_mut_mapping);
+    Py_XDECREF(collections_abc_mut_multi_mapping);
+
+    return NULL;
+
+#undef WITH_MOD
+#undef GET_MOD_ATTR
+}
diff --git a/third_party/python/multidict/multidict/_multidict_base.py b/third_party/python/multidict/multidict/_multidict_base.py
new file mode 100644
index 0000000000..394466548c
--- /dev/null
+++ b/third_party/python/multidict/multidict/_multidict_base.py
@@ -0,0 +1,144 @@
+from collections.abc import ItemsView, Iterable, KeysView, Set, ValuesView
+
+
+def _abc_itemsview_register(view_cls):
+    ItemsView.register(view_cls)
+
+
+def _abc_keysview_register(view_cls):
+    KeysView.register(view_cls)
+
+
+def _abc_valuesview_register(view_cls):
+    ValuesView.register(view_cls)
+
+
+def _viewbaseset_richcmp(view, other, op):
+    if op == 0:  # <
+        if not isinstance(other, Set):
+            return NotImplemented
+        return len(view) < len(other) and view <= other
+    elif op == 1:  # <=
+        if not isinstance(other, Set):
+            return NotImplemented
+        if len(view) > len(other):
+            return False
+        for elem in view:
+            if elem not in other:
+                return False
+        return True
+    elif op == 2:  # ==
+        if not isinstance(other, Set):
+            return NotImplemented
+        return len(view) == len(other) and view <= other
+    elif op == 3:  # !=
+        return not view == other
+    elif op == 4:  # >
+        if not isinstance(other, Set):
+            return NotImplemented
+        return len(view) > len(other) and view >= other
+    elif op == 5:  # >=
+        if not isinstance(other, Set):
+            return NotImplemented
+        if len(view) < len(other):
+            return False
+        for elem in other:
+            if elem not in view:
+                return False
+        return True
+
+
+def _viewbaseset_and(view, other):
+    if not isinstance(other, Iterable):
+        return NotImplemented
+    if isinstance(view, Set):
+        view = set(iter(view))
+    if isinstance(other, Set):
+        other = set(iter(other))
+    if not isinstance(other, Set):
+        other = set(iter(other))
+    return view & other
+
+
+def _viewbaseset_or(view, other):
+    if not isinstance(other, Iterable):
+        return NotImplemented
+    if isinstance(view, Set):
+        view = set(iter(view))
+    if isinstance(other, Set):
+        other = set(iter(other))
+    if not isinstance(other, Set):
+        other = set(iter(other))
+    return view | other
+
+
+def _viewbaseset_sub(view, other):
+    if not isinstance(other, Iterable):
+        return NotImplemented
+    if isinstance(view, Set):
+        view = set(iter(view))
+    if isinstance(other, Set):
+        other = set(iter(other))
+    if not isinstance(other, Set):
+        other = set(iter(other))
+    return view - other
+
+
+def _viewbaseset_xor(view, other):
+    if not isinstance(other, Iterable):
+        return NotImplemented
+    if isinstance(view, Set):
+        view = set(iter(view))
+    if isinstance(other, Set):
+        other = set(iter(other))
+    if not isinstance(other, Set):
+        other = set(iter(other))
+    return view ^ other
+
+
+def _itemsview_isdisjoint(view, other):
+    "Return True if two sets have a null intersection."
+    for v in other:
+        if v in view:
+            return False
+    return True
+
+
+def _itemsview_repr(view):
+    lst = []
+    for k, v in view:
+        lst.append("{!r}: {!r}".format(k, v))
+    body = ", ".join(lst)
+    return "{}({})".format(view.__class__.__name__, body)
+
+
+def _keysview_isdisjoint(view, other):
+    "Return True if two sets have a null intersection."
+    for k in other:
+        if k in view:
+            return False
+    return True
+
+
+def _keysview_repr(view):
+    lst = []
+    for k in view:
+        lst.append("{!r}".format(k))
+    body = ", ".join(lst)
+    return "{}({})".format(view.__class__.__name__, body)
+
+
+def _valuesview_repr(view):
+    lst = []
+    for v in view:
+        lst.append("{!r}".format(v))
+    body = ", ".join(lst)
+    return "{}({})".format(view.__class__.__name__, body)
+
+
+def _mdrepr(md):
+    lst = []
+    for k, v in md.items():
+        lst.append("'{}': {!r}".format(k, v))
+    body = ", ".join(lst)
+    return "<{}({})>".format(md.__class__.__name__, body)
diff --git a/third_party/python/multidict/multidict/_multidict_py.py b/third_party/python/multidict/multidict/_multidict_py.py
new file mode 100644
index 0000000000..1ec63da0d5
--- /dev/null
+++ b/third_party/python/multidict/multidict/_multidict_py.py
@@ -0,0 +1,515 @@
+import sys
+from array import array
+from collections import abc
+
+from ._abc import MultiMapping, MutableMultiMapping
+
+_marker = object()
+
+
+class istr(str):
+
+    """Case insensitive str."""
+
+    __is_istr__ = True
+
+
+upstr = istr  # for relaxing backward compatibility problems
+
+
+def getversion(md):
+    if not isinstance(md, _Base):
+        raise TypeError("Parameter should be multidict or proxy")
+    return md._impl._version
+
+
+_version = array("Q", [0])
+
+
+class _Impl:
+    __slots__ = ("_items", "_version")
+
+    def __init__(self):
+        self._items = []
+        self.incr_version()
+
+    def incr_version(self):
+        global _version
+        v = _version
+        v[0] += 1
+        self._version = v[0]
+
+    if sys.implementation.name != "pypy":
+
+        def __sizeof__(self):
+            return object.__sizeof__(self) + sys.getsizeof(self._items)
+
+
+class _Base:
+    def _title(self, key):
+        return key
+
+    def getall(self, key, default=_marker):
+        """Return a list of all values matching the key."""
+        identity = self._title(key)
+        res = [v for i, k, v in self._impl._items if i == identity]
+        if res:
+            return res
+        if not res and default is not _marker:
+            return default
+        raise KeyError("Key not found: %r" % key)
+
+    def getone(self, key, default=_marker):
+        """Get first value matching the key."""
+        identity = self._title(key)
+        for i, k, v in self._impl._items:
+            if i == identity:
+                return v
+        if default is not _marker:
+            return default
+        raise KeyError("Key not found: %r" % key)
+
+    # Mapping interface #
+
+    def __getitem__(self, key):
+        return self.getone(key)
+
+    def get(self, key, default=None):
+        """Get first value matching the key.
+
+        The method is alias for .getone().
+        """
+        return self.getone(key, default)
+
+    def __iter__(self):
+        return iter(self.keys())
+
+    def __len__(self):
+        return len(self._impl._items)
+
+    def keys(self):
+        """Return a new view of the dictionary's keys."""
+        return _KeysView(self._impl)
+
+    def items(self):
+        """Return a new view of the dictionary's items *(key, value) pairs)."""
+        return _ItemsView(self._impl)
+
+    def values(self):
+        """Return a new view of the dictionary's values."""
+        return _ValuesView(self._impl)
+
+    def __eq__(self, other):
+        if not isinstance(other, abc.Mapping):
+            return NotImplemented
+        if isinstance(other, _Base):
+            lft = self._impl._items
+            rht = other._impl._items
+            if len(lft) != len(rht):
+                return False
+            for (i1, k2, v1), (i2, k2, v2) in zip(lft, rht):
+                if i1 != i2 or v1 != v2:
+                    return False
+            return True
+        if len(self._impl._items) != len(other):
+            return False
+        for k, v in self.items():
+            nv = other.get(k, _marker)
+            if v != nv:
+                return False
+        return True
+
+    def __contains__(self, key):
+        identity = self._title(key)
+        for i, k, v in self._impl._items:
+            if i == identity:
+                return True
+        return False
+
+    def __repr__(self):
+        body = ", ".join("'{}': {!r}".format(k, v) for k, v in self.items())
+        return "<{}({})>".format(self.__class__.__name__, body)
+
+
+class MultiDictProxy(_Base, MultiMapping):
+    """Read-only proxy for MultiDict instance."""
+
+    def __init__(self, arg):
+        if not isinstance(arg, (MultiDict, MultiDictProxy)):
+            raise TypeError(
+                "ctor requires MultiDict or MultiDictProxy instance"
+                ", not {}".format(type(arg))
+            )
+
+        self._impl = arg._impl
+
+    def __reduce__(self):
+        raise TypeError("can't pickle {} objects".format(self.__class__.__name__))
+
+    def copy(self):
+        """Return a copy of itself."""
+        return MultiDict(self.items())
+
+
+class CIMultiDictProxy(MultiDictProxy):
+    """Read-only proxy for CIMultiDict instance."""
+
+    def __init__(self, arg):
+        if not isinstance(arg, (CIMultiDict, CIMultiDictProxy)):
+            raise TypeError(
+                "ctor requires CIMultiDict or CIMultiDictProxy instance"
+                ", not {}".format(type(arg))
+            )
+
+        self._impl = arg._impl
+
+    def _title(self, key):
+        return key.title()
+
+    def copy(self):
+        """Return a copy of itself."""
+        return CIMultiDict(self.items())
+
+
+class MultiDict(_Base, MutableMultiMapping):
+    """Dictionary with the support for duplicate keys."""
+
+    def __init__(self, *args, **kwargs):
+        self._impl = _Impl()
+
+        self._extend(args, kwargs, self.__class__.__name__, self._extend_items)
+
+    if sys.implementation.name != "pypy":
+
+        def __sizeof__(self):
+            return object.__sizeof__(self) + sys.getsizeof(self._impl)
+
+    def __reduce__(self):
+        return (self.__class__, (list(self.items()),))
+
+    def _title(self, key):
+        return key
+
+    def _key(self, key):
+        if isinstance(key, str):
+            return key
+        else:
+            raise TypeError(
+                "MultiDict keys should be either str " "or subclasses of str"
+            )
+
+    def add(self, key, value):
+        identity = self._title(key)
+        self._impl._items.append((identity, self._key(key), value))
+        self._impl.incr_version()
+
+    def copy(self):
+        """Return a copy of itself."""
+        cls = self.__class__
+        return cls(self.items())
+
+    __copy__ = copy
+
+    def extend(self, *args, **kwargs):
+        """Extend current MultiDict with more values.
+
+        This method must be used instead of update.
+        """
+        self._extend(args, kwargs, "extend", self._extend_items)
+
+    def _extend(self, args, kwargs, name, method):
+        if len(args) > 1:
+            raise TypeError(
+                "{} takes at most 1 positional argument"
+                " ({} given)".format(name, len(args))
+            )
+        if args:
+            arg = args[0]
+            if isinstance(args[0], (MultiDict, MultiDictProxy)) and not kwargs:
+                items = arg._impl._items
+            else:
+                if hasattr(arg, "items"):
+                    arg = arg.items()
+                if kwargs:
+                    arg = list(arg)
+                    arg.extend(list(kwargs.items()))
+                items = []
+                for item in arg:
+                    if not len(item) == 2:
+                        raise TypeError(
+                            "{} takes either dict or list of (key, value) "
+                            "tuples".format(name)
+                        )
+                    items.append((self._title(item[0]), self._key(item[0]), item[1]))
+
+            method(items)
+        else:
+            method(
+                [
+                    (self._title(key), self._key(key), value)
+                    for key, value in kwargs.items()
+                ]
+            )
+
+    def _extend_items(self, items):
+        for identity, key, value in items:
+            self.add(key, value)
+
+    def clear(self):
+        """Remove all items from MultiDict."""
+        self._impl._items.clear()
+        self._impl.incr_version()
+
+    # Mapping interface #
+
+    def __setitem__(self, key, value):
+        self._replace(key, value)
+
+    def __delitem__(self, key):
+        identity = self._title(key)
+        items = self._impl._items
+        found = False
+        for i in range(len(items) - 1, -1, -1):
+            if items[i][0] == identity:
+                del items[i]
+                found = True
+        if not found:
+            raise KeyError(key)
+        else:
+            self._impl.incr_version()
+
+    def setdefault(self, key, default=None):
+        """Return value for key, set value to default if key is not present."""
+        identity = self._title(key)
+        for i, k, v in self._impl._items:
+            if i == identity:
+                return v
+        self.add(key, default)
+        return default
+
+    def popone(self, key, default=_marker):
+        """Remove specified key and return the corresponding value.
+
+        If key is not found, d is returned if given, otherwise
+        KeyError is raised.
+
+        """
+        identity = self._title(key)
+        for i in range(len(self._impl._items)):
+            if self._impl._items[i][0] == identity:
+                value = self._impl._items[i][2]
+                del self._impl._items[i]
+                self._impl.incr_version()
+                return value
+        if default is _marker:
+            raise KeyError(key)
+        else:
+            return default
+
+    pop = popone  # type: ignore
+
+    def popall(self, key, default=_marker):
+        """Remove all occurrences of key and return the list of corresponding
+        values.
+
+        If key is not found, default is returned if given, otherwise
+        KeyError is raised.
+
+        """
+        found = False
+        identity = self._title(key)
+        ret = []
+        for i in range(len(self._impl._items) - 1, -1, -1):
+            item = self._impl._items[i]
+            if item[0] == identity:
+                ret.append(item[2])
+                del self._impl._items[i]
+                self._impl.incr_version()
+                found = True
+        if not found:
+            if default is _marker:
+                raise KeyError(key)
+            else:
+                return default
+        else:
+            ret.reverse()
+            return ret
+
+    def popitem(self):
+        """Remove and return an arbitrary (key, value) pair."""
+        if self._impl._items:
+            i = self._impl._items.pop(0)
+            self._impl.incr_version()
+            return i[1], i[2]
+        else:
+            raise KeyError("empty multidict")
+
+    def update(self, *args, **kwargs):
+        """Update the dictionary from *other*, overwriting existing keys."""
+        self._extend(args, kwargs, "update", self._update_items)
+
+    def _update_items(self, items):
+        if not items:
+            return
+        used_keys = {}
+        for identity, key, value in items:
+            start = used_keys.get(identity, 0)
+            for i in range(start, len(self._impl._items)):
+                item = self._impl._items[i]
+                if item[0] == identity:
+                    used_keys[identity] = i + 1
+                    self._impl._items[i] = (identity, key, value)
+                    break
+            else:
+                self._impl._items.append((identity, key, value))
+                used_keys[identity] = len(self._impl._items)
+
+        # drop tails
+        i = 0
+        while i < len(self._impl._items):
+            item = self._impl._items[i]
+            identity = item[0]
+            pos = used_keys.get(identity)
+            if pos is None:
+                i += 1
+                continue
+            if i >= pos:
+                del self._impl._items[i]
+            else:
+                i += 1
+
+        self._impl.incr_version()
+
+    def _replace(self, key, value):
+        key = self._key(key)
+        identity = self._title(key)
+        items = self._impl._items
+
+        for i in range(len(items)):
+            item = items[i]
+            if item[0] == identity:
+                items[i] = (identity, key, value)
+                # i points to last found item
+                rgt = i
+                self._impl.incr_version()
+                break
+        else:
+            self._impl._items.append((identity, key, value))
+            self._impl.incr_version()
+            return
+
+        # remove all tail items
+        i = rgt + 1
+        while i < len(items):
+            item = items[i]
+            if item[0] == identity:
+                del items[i]
+            else:
+                i += 1
+
+
+class CIMultiDict(MultiDict):
+    """Dictionary with the support for duplicate case-insensitive keys."""
+
+    def _title(self, key):
+        return key.title()
+
+
+class _Iter:
+    __slots__ = ("_size", "_iter")
+
+    def __init__(self, size, iterator):
+        self._size = size
+        self._iter = iterator
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        return next(self._iter)
+
+    def __length_hint__(self):
+        return self._size
+
+
+class _ViewBase:
+    def __init__(self, impl):
+        self._impl = impl
+        self._version = impl._version
+
+    def __len__(self):
+        return len(self._impl._items)
+
+
+class _ItemsView(_ViewBase, abc.ItemsView):
+    def __contains__(self, item):
+        assert isinstance(item, tuple) or isinstance(item, list)
+        assert len(item) == 2
+        for i, k, v in self._impl._items:
+            if item[0] == k and item[1] == v:
+                return True
+        return False
+
+    def __iter__(self):
+        return _Iter(len(self), self._iter())
+
+    def _iter(self):
+        for i, k, v in self._impl._items:
+            if self._version != self._impl._version:
+                raise RuntimeError("Dictionary changed during iteration")
+            yield k, v
+
+    def __repr__(self):
+        lst = []
+        for item in self._impl._items:
+            lst.append("{!r}: {!r}".format(item[1], item[2]))
+        body = ", ".join(lst)
+        return "{}({})".format(self.__class__.__name__, body)
+
+
+class _ValuesView(_ViewBase, abc.ValuesView):
+    def __contains__(self, value):
+        for item in self._impl._items:
+            if item[2] == value:
+                return True
+        return False
+
+    def __iter__(self):
+        return _Iter(len(self), self._iter())
+
+    def _iter(self):
+        for item in self._impl._items:
+            if self._version != self._impl._version:
+                raise RuntimeError("Dictionary changed during iteration")
+            yield item[2]
+
+    def __repr__(self):
+        lst = []
+        for item in self._impl._items:
+            lst.append("{!r}".format(item[2]))
+        body = ", ".join(lst)
+        return "{}({})".format(self.__class__.__name__, body)
+
+
+class _KeysView(_ViewBase, abc.KeysView):
+    def __contains__(self, key):
+        for item in self._impl._items:
+            if item[1] == key:
+                return True
+        return False
+
+    def __iter__(self):
+        return _Iter(len(self), self._iter())
+
+    def _iter(self):
+        for item in self._impl._items:
+            if self._version != self._impl._version:
+                raise RuntimeError("Dictionary changed during iteration")
+            yield item[1]
+
+    def __repr__(self):
+        lst = []
+        for item in self._impl._items:
+            lst.append("{!r}".format(item[1]))
+        body = ", ".join(lst)
+        return "{}({})".format(self.__class__.__name__, body)
diff --git a/third_party/python/multidict/multidict/_multilib/defs.h b/third_party/python/multidict/multidict/_multilib/defs.h
new file mode 100644
index 0000000000..c7027c817e
--- /dev/null
+++ b/third_party/python/multidict/multidict/_multilib/defs.h
@@ -0,0 +1,22 @@
+#ifndef _MULTIDICT_DEFS_H
+#define _MULTIDICT_DEFS_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+_Py_IDENTIFIER(lower);
+
+/* We link this module statically for convenience.  If compiled as a shared
+   library instead, some compilers don't allow addresses of Python objects
+   defined in other libraries to be used in static initializers here.  The
+   DEFERRED_ADDRESS macro is used to tag the slots where such addresses
+   appear; the module init function must fill in the tagged slots at runtime.
+   The argument is for documentation -- the macro ignores it.
+*/
+#define DEFERRED_ADDRESS(ADDR) 0
+
+#ifdef __cplusplus
+}
+#endif
+#endif
diff --git a/third_party/python/multidict/multidict/_multilib/dict.h b/third_party/python/multidict/multidict/_multilib/dict.h
new file mode 100644
index 0000000000..3caf83e5b4
--- /dev/null
+++ b/third_party/python/multidict/multidict/_multilib/dict.h
@@ -0,0 +1,24 @@
+#ifndef _MULTIDICT_C_H
+#define _MULTIDICT_C_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct {  // 16 or 24 for GC prefix
+    PyObject_HEAD  // 16
+    PyObject *weaklist;
+    pair_list_t pairs;
+} MultiDictObject;
+
+typedef struct {
+    PyObject_HEAD
+    PyObject *weaklist;
+    MultiDictObject *md;
+} MultiDictProxyObject;
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/third_party/python/multidict/multidict/_multilib/istr.h b/third_party/python/multidict/multidict/_multilib/istr.h
new file mode 100644
index 0000000000..2688f48914
--- /dev/null
+++ b/third_party/python/multidict/multidict/_multilib/istr.h
@@ -0,0 +1,85 @@
+#ifndef _MULTIDICT_ISTR_H
+#define _MULTIDICT_ISTR_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct {
+    PyUnicodeObject str;
+    PyObject * canonical;
+} istrobject;
+
+PyDoc_STRVAR(istr__doc__, "istr class implementation");
+
+static PyTypeObject istr_type;
+
+static inline void
+istr_dealloc(istrobject *self)
+{
+    Py_XDECREF(self->canonical);
+    PyUnicode_Type.tp_dealloc((PyObject*)self);
+}
+
+static inline PyObject *
+istr_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
+{
+    PyObject *x = NULL;
+    static char *kwlist[] = {"object", "encoding", "errors", 0};
+    PyObject *encoding = NULL;
+    PyObject *errors = NULL;
+    PyObject *s = NULL;
+    PyObject * ret = NULL;
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "|OOO:str",
+                                     kwlist, &x, &encoding, &errors)) {
+        return NULL;
+    }
+    if (x != NULL && Py_TYPE(x) == &istr_type) {
+        Py_INCREF(x);
+        return x;
+    }
+    ret = PyUnicode_Type.tp_new(type, args, kwds);
+    if (!ret) {
+        goto fail;
+    }
+    s =_PyObject_CallMethodId(ret, &PyId_lower, NULL);
+    if (!s) {
+        goto fail;
+    }
+    ((istrobject*)ret)->canonical = s;
+    s = NULL;  /* the reference is stollen by .canonical */
+    return ret;
+fail:
+    Py_XDECREF(ret);
+    return NULL;
+}
+
+static PyTypeObject istr_type = {
+    PyVarObject_HEAD_INIT(DEFERRED_ADDRESS(&PyType_Type), 0)
+    "multidict._multidict.istr",
+    sizeof(istrobject),
+    .tp_dealloc = (destructor)istr_dealloc,
+    .tp_flags = Py_TPFLAGS_DEFAULT
+              | Py_TPFLAGS_BASETYPE
+              | Py_TPFLAGS_UNICODE_SUBCLASS,
+    .tp_doc = istr__doc__,
+    .tp_base = DEFERRED_ADDRESS(&PyUnicode_Type),
+    .tp_new = (newfunc)istr_new,
+};
+
+
+static inline int
+istr_init(void)
+{
+    istr_type.tp_base = &PyUnicode_Type;
+    if (PyType_Ready(&istr_type) < 0) {
+        return -1;
+    }
+    return 0;
+}
+
+#ifdef __cplusplus
+}
+#endif
+#endif
diff --git a/third_party/python/multidict/multidict/_multilib/iter.h b/third_party/python/multidict/multidict/_multilib/iter.h
new file mode 100644
index 0000000000..4e2e32b387
--- /dev/null
+++ b/third_party/python/multidict/multidict/_multilib/iter.h
@@ -0,0 +1,238 @@
+#ifndef _MULTIDICT_ITER_H
+#define _MULTIDICT_ITER_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+static PyTypeObject multidict_items_iter_type;
+static PyTypeObject multidict_values_iter_type;
+static PyTypeObject multidict_keys_iter_type;
+
+typedef struct multidict_iter {
+    PyObject_HEAD
+    MultiDictObject *md;  // MultiDict or CIMultiDict
+    Py_ssize_t current;
+    uint64_t version;
+} MultidictIter;
+
+static inline void
+_init_iter(MultidictIter *it, MultiDictObject *md)
+{
+    Py_INCREF(md);
+
+    it->md = md;
+    it->current = 0;
+    it->version = pair_list_version(&md->pairs);
+}
+
+static inline PyObject *
+multidict_items_iter_new(MultiDictObject *md)
+{
+    MultidictIter *it = PyObject_GC_New(
+        MultidictIter, &multidict_items_iter_type);
+    if (it == NULL) {
+        return NULL;
+    }
+
+    _init_iter(it, md);
+
+    PyObject_GC_Track(it);
+    return (PyObject *)it;
+}
+
+static inline PyObject *
+multidict_keys_iter_new(MultiDictObject *md)
+{
+    MultidictIter *it = PyObject_GC_New(
+        MultidictIter, &multidict_keys_iter_type);
+    if (it == NULL) {
+        return NULL;
+    }
+
+    _init_iter(it, md);
+
+    PyObject_GC_Track(it);
+    return (PyObject *)it;
+}
+
+static inline PyObject *
+multidict_values_iter_new(MultiDictObject *md)
+{
+    MultidictIter *it = PyObject_GC_New(
+        MultidictIter, &multidict_values_iter_type);
+    if (it == NULL) {
+        return NULL;
+    }
+
+    _init_iter(it, md);
+
+    PyObject_GC_Track(it);
+    return (PyObject *)it;
+}
+
+static inline PyObject *
+multidict_items_iter_iternext(MultidictIter *self)
+{
+    PyObject *key = NULL;
+    PyObject *value = NULL;
+    PyObject *ret = NULL;
+
+    if (self->version != pair_list_version(&self->md->pairs)) {
+        PyErr_SetString(PyExc_RuntimeError, "Dictionary changed during iteration");
+        return NULL;
+    }
+
+    if (!_pair_list_next(&self->md->pairs, &self->current, NULL, &key, &value, NULL)) {
+        PyErr_SetNone(PyExc_StopIteration);
+        return NULL;
+    }
+
+    ret = PyTuple_Pack(2, key, value);
+    if (ret == NULL) {
+        return NULL;
+    }
+
+    return ret;
+}
+
+static inline PyObject *
+multidict_values_iter_iternext(MultidictIter *self)
+{
+    PyObject *value = NULL;
+
+    if (self->version != pair_list_version(&self->md->pairs)) {
+        PyErr_SetString(PyExc_RuntimeError, "Dictionary changed during iteration");
+        return NULL;
+    }
+
+    if (!pair_list_next(&self->md->pairs, &self->current, NULL, NULL, &value)) {
+        PyErr_SetNone(PyExc_StopIteration);
+        return NULL;
+    }
+
+    Py_INCREF(value);
+
+    return value;
+}
+
+static inline PyObject *
+multidict_keys_iter_iternext(MultidictIter *self)
+{
+    PyObject *key = NULL;
+
+    if (self->version != pair_list_version(&self->md->pairs)) {
+        PyErr_SetString(PyExc_RuntimeError, "Dictionary changed during iteration");
+        return NULL;
+    }
+
+    if (!pair_list_next(&self->md->pairs, &self->current, NULL, &key, NULL)) {
+        PyErr_SetNone(PyExc_StopIteration);
+        return NULL;
+    }
+
+    Py_INCREF(key);
+
+    return key;
+}
+
+static inline void
+multidict_iter_dealloc(MultidictIter *self)
+{
+    PyObject_GC_UnTrack(self);
+    Py_XDECREF(self->md);
+    PyObject_GC_Del(self);
+}
+
+static inline int
+multidict_iter_traverse(MultidictIter *self, visitproc visit, void *arg)
+{
+    Py_VISIT(self->md);
+    return 0;
+}
+
+static inline int
+multidict_iter_clear(MultidictIter *self)
+{
+    Py_CLEAR(self->md);
+    return 0;
+}
+
+static inline PyObject *
+multidict_iter_len(MultidictIter *self)
+{
+    return PyLong_FromLong(pair_list_len(&self->md->pairs));
+}
+
+PyDoc_STRVAR(length_hint_doc,
+             "Private method returning an estimate of len(list(it)).");
+
+static PyMethodDef multidict_iter_methods[] = {
+    {
+        "__length_hint__",
+        (PyCFunction)(void(*)(void))multidict_iter_len,
+        METH_NOARGS,
+        length_hint_doc
+    },
+    {
+        NULL,
+        NULL
+    }   /* sentinel */
+};
+
+/***********************************************************************/
+
+static PyTypeObject multidict_items_iter_type = {
+    PyVarObject_HEAD_INIT(DEFERRED_ADDRESS(&PyType_Type), 0)
+    "multidict._multidict._itemsiter",         /* tp_name */
+    sizeof(MultidictIter),                     /* tp_basicsize */
+    .tp_dealloc = (destructor)multidict_iter_dealloc,
+    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,
+    .tp_traverse = (traverseproc)multidict_iter_traverse,
+    .tp_clear = (inquiry)multidict_iter_clear,
+    .tp_iter = PyObject_SelfIter,
+    .tp_iternext = (iternextfunc)multidict_items_iter_iternext,
+    .tp_methods = multidict_iter_methods,
+};
+
+static PyTypeObject multidict_values_iter_type = {
+    PyVarObject_HEAD_INIT(DEFERRED_ADDRESS(&PyType_Type), 0)
+    "multidict._multidict._valuesiter",         /* tp_name */
+    sizeof(MultidictIter),                      /* tp_basicsize */
+    .tp_dealloc = (destructor)multidict_iter_dealloc,
+    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,
+    .tp_traverse = (traverseproc)multidict_iter_traverse,
+    .tp_clear = (inquiry)multidict_iter_clear,
+    .tp_iter = PyObject_SelfIter,
+    .tp_iternext = (iternextfunc)multidict_values_iter_iternext,
+    .tp_methods = multidict_iter_methods,
+};
+
+static PyTypeObject multidict_keys_iter_type = {
+    PyVarObject_HEAD_INIT(DEFERRED_ADDRESS(&PyType_Type), 0)
+    "multidict._multidict._keysiter",         /* tp_name */
+    sizeof(MultidictIter),                    /* tp_basicsize */
+    .tp_dealloc = (destructor)multidict_iter_dealloc,
+    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,
+    .tp_traverse = (traverseproc)multidict_iter_traverse,
+    .tp_clear = (inquiry)multidict_iter_clear,
+    .tp_iter = PyObject_SelfIter,
+    .tp_iternext = (iternextfunc)multidict_keys_iter_iternext,
+    .tp_methods = multidict_iter_methods,
+};
+
+static inline int
+multidict_iter_init()
+{
+    if (PyType_Ready(&multidict_items_iter_type) < 0 ||
+        PyType_Ready(&multidict_values_iter_type) < 0 ||
+        PyType_Ready(&multidict_keys_iter_type) < 0) {
+        return -1;
+    }
+    return 0;
+}
+
+#ifdef __cplusplus
+}
+#endif
+#endif
diff --git a/third_party/python/multidict/multidict/_multilib/pair_list.h b/third_party/python/multidict/multidict/_multilib/pair_list.h
new file mode 100644
index 0000000000..7eafd215b5
--- /dev/null
+++ b/third_party/python/multidict/multidict/_multilib/pair_list.h
@@ -0,0 +1,1244 @@
+#ifndef _MULTIDICT_PAIR_LIST_H
+#define _MULTIDICT_PAIR_LIST_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <string.h>
+#include <stddef.h>
+#include <stdint.h>
+
+typedef PyObject * (*calc_identity_func)(PyObject *key);
+
+typedef struct pair {
+    PyObject  *identity;  // 8
+    PyObject  *key;       // 8
+    PyObject  *value;     // 8
+    Py_hash_t  hash;      // 8
+} pair_t;
+
+/* Note about the structure size
+With 29 pairs the MultiDict object size is slightly less than 1KiB
+(1000-1008 bytes depending on Python version,
+plus extra 12 bytes for memory allocator internal structures).
+As the result the max reserved size is 1020 bytes at most.
+
+To fit into 512 bytes, the structure can contain only 13 pairs
+which is too small, e.g. https://www.python.org returns 16 headers
+(9 of them are caching proxy information though).
+
+The embedded buffer intention is to fit the vast majority of possible
+HTTP headers into the buffer without allocating an extra memory block.
+*/
+
+#if (PY_VERSION_HEX < 0x03080000)
+#define EMBEDDED_CAPACITY 28
+#else
+#define EMBEDDED_CAPACITY 29
+#endif
+
+typedef struct pair_list {  // 40
+    Py_ssize_t  capacity;   // 8
+    Py_ssize_t  size;       // 8
+    uint64_t  version;      // 8
+    calc_identity_func calc_identity;  // 8
+    pair_t *pairs;          // 8
+    pair_t buffer[EMBEDDED_CAPACITY];
+} pair_list_t;
+
+#define MIN_CAPACITY 63
+#define CAPACITY_STEP 64
+
+/* Global counter used to set ma_version_tag field of dictionary.
+ * It is incremented each time that a dictionary is created and each
+ * time that a dictionary is modified. */
+static uint64_t pair_list_global_version = 0;
+
+#define NEXT_VERSION() (++pair_list_global_version)
+
+
+static inline int
+str_cmp(PyObject *s1, PyObject *s2)
+{
+    PyObject *ret = PyUnicode_RichCompare(s1, s2, Py_EQ);
+    if (ret == Py_True) {
+        Py_DECREF(ret);
+        return 1;
+    }
+    else if (ret == NULL) {
+        return -1;
+    }
+    else {
+        Py_DECREF(ret);
+        return 0;
+    }
+}
+
+
+static inline PyObject *
+key_to_str(PyObject *key)
+{
+    PyObject *ret;
+    PyTypeObject *type = Py_TYPE(key);
+    if (type == &istr_type) {
+        ret = ((istrobject*)key)->canonical;
+        Py_INCREF(ret);
+        return ret;
+    }
+    if (PyUnicode_CheckExact(key)) {
+        Py_INCREF(key);
+        return key;
+    }
+    if (PyUnicode_Check(key)) {
+        return PyObject_Str(key);
+    }
+    PyErr_SetString(PyExc_TypeError,
+                    "MultiDict keys should be either str "
+                    "or subclasses of str");
+    return NULL;
+}
+
+
+static inline PyObject *
+ci_key_to_str(PyObject *key)
+{
+    PyObject *ret;
+    PyTypeObject *type = Py_TYPE(key);
+    if (type == &istr_type) {
+        ret = ((istrobject*)key)->canonical;
+        Py_INCREF(ret);
+        return ret;
+    }
+    if (PyUnicode_Check(key)) {
+        return _PyObject_CallMethodId(key, &PyId_lower, NULL);
+    }
+    PyErr_SetString(PyExc_TypeError,
+                    "CIMultiDict keys should be either str "
+                    "or subclasses of str");
+    return NULL;
+}
+
+static inline pair_t *
+pair_list_get(pair_list_t *list, Py_ssize_t i)
+{
+    pair_t *item = list->pairs + i;
+    return item;
+}
+
+
+static inline int
+pair_list_grow(pair_list_t *list)
+{
+    // Grow by one element if needed
+    Py_ssize_t new_capacity;
+    pair_t *new_pairs;
+
+    if (list->size < list->capacity) {
+        return 0;
+    }
+
+    if (list->pairs == list->buffer) {
+        new_pairs = PyMem_New(pair_t, MIN_CAPACITY);
+        memcpy(new_pairs, list->buffer, (size_t)list->capacity * sizeof(pair_t));
+
+        list->pairs = new_pairs;
+        list->capacity = MIN_CAPACITY;
+        return 0;
+    } else {
+        new_capacity = list->capacity + CAPACITY_STEP;
+        new_pairs = PyMem_Resize(list->pairs, pair_t, (size_t)new_capacity);
+
+        if (NULL == new_pairs) {
+            // Resizing error
+            return -1;
+        }
+
+        list->pairs = new_pairs;
+        list->capacity = new_capacity;
+        return 0;
+    }
+}
+
+
+static inline int
+pair_list_shrink(pair_list_t *list)
+{
+    // Shrink by one element if needed.
+    // Optimization is applied to prevent jitter
+    // (grow-shrink-grow-shrink on adding-removing the single element
+    // when the buffer is full).
+    // To prevent this, the buffer is resized if the size is less than the capacity
+    // by 2*CAPACITY_STEP factor.
+    // The switch back to embedded buffer is never performed for both reasons:
+    // the code simplicity and the jitter prevention.
+
+    pair_t *new_pairs;
+    Py_ssize_t new_capacity;
+
+    if (list->capacity - list->size < 2 * CAPACITY_STEP) {
+        return 0;
+    }
+    new_capacity = list->capacity - CAPACITY_STEP;
+    if (new_capacity < MIN_CAPACITY) {
+        return 0;
+    }
+
+    new_pairs = PyMem_Resize(list->pairs, pair_t, (size_t)new_capacity);
+
+    if (NULL == new_pairs) {
+        // Resizing error
+        return -1;
+    }
+
+    list->pairs = new_pairs;
+    list->capacity = new_capacity;
+
+    return 0;
+}
+
+
+static inline int
+_pair_list_init(pair_list_t *list, calc_identity_func calc_identity)
+{
+    list->pairs = list->buffer;
+    list->capacity = EMBEDDED_CAPACITY;
+    list->size = 0;
+    list->version = NEXT_VERSION();
+    list->calc_identity = calc_identity;
+    return 0;
+}
+
+static inline int
+pair_list_init(pair_list_t *list)
+{
+    return _pair_list_init(list, key_to_str);
+}
+
+
+static inline int
+ci_pair_list_init(pair_list_t *list)
+{
+    return _pair_list_init(list, ci_key_to_str);
+}
+
+
+static inline void
+pair_list_dealloc(pair_list_t *list)
+{
+    pair_t *pair;
+    Py_ssize_t pos;
+
+    for (pos = 0; pos < list->size; pos++) {
+        pair = pair_list_get(list, pos);
+
+        Py_XDECREF(pair->identity);
+        Py_XDECREF(pair->key);
+        Py_XDECREF(pair->value);
+    }
+
+    /*
+    Strictly speaking, resetting size and capacity and
+    assigning pairs to buffer is not necessary.
+    Do it to consistency and idemotency.
+    The cleanup doesn't hurt performance.
+    !!!
+    !!! The buffer deletion is crucial though.
+    !!!
+    */
+    list->size = 0;
+    if (list->pairs != list->buffer) {
+        PyMem_Del(list->pairs);
+        list->pairs = list->buffer;
+        list->capacity = EMBEDDED_CAPACITY;
+    }
+}
+
+
+static inline Py_ssize_t
+pair_list_len(pair_list_t *list)
+{
+    return list->size;
+}
+
+
+static inline int
+_pair_list_add_with_hash(pair_list_t *list,
+                         PyObject *identity,
+                         PyObject *key,
+                         PyObject *value,
+                         Py_hash_t hash)
+{
+    pair_t *pair;
+
+    if (pair_list_grow(list) < 0) {
+        return -1;
+    }
+
+    pair = pair_list_get(list, list->size);
+
+    Py_INCREF(identity);
+    pair->identity = identity;
+
+    Py_INCREF(key);
+    pair->key = key;
+
+    Py_INCREF(value);
+    pair->value = value;
+
+    pair->hash = hash;
+
+    list->version = NEXT_VERSION();
+    list->size += 1;
+
+    return 0;
+}
+
+
+static inline int
+pair_list_add(pair_list_t *list,
+              PyObject *key,
+              PyObject *value)
+{
+    Py_hash_t hash;
+    PyObject *identity = NULL;
+    int ret;
+
+    identity = list->calc_identity(key);
+    if (identity == NULL) {
+        goto fail;
+    }
+    hash = PyObject_Hash(identity);
+    if (hash == -1) {
+        goto fail;
+    }
+    ret = _pair_list_add_with_hash(list, identity, key, value, hash);
+    Py_DECREF(identity);
+    return ret;
+fail:
+    Py_XDECREF(identity);
+    return -1;
+}
+
+
+static inline int
+pair_list_del_at(pair_list_t *list, Py_ssize_t pos)
+{
+    // return 1 on success, -1 on failure
+    Py_ssize_t tail;
+    pair_t *pair;
+
+    pair = pair_list_get(list, pos);
+    Py_DECREF(pair->identity);
+    Py_DECREF(pair->key);
+    Py_DECREF(pair->value);
+
+    list->size -= 1;
+    list->version = NEXT_VERSION();
+
+    if (list->size == pos) {
+        // remove from tail, no need to shift body
+        return 0;
+    }
+
+    tail = list->size - pos;
+    // TODO: raise an error if tail < 0
+    memmove((void *)pair_list_get(list, pos),
+            (void *)pair_list_get(list, pos + 1),
+            sizeof(pair_t) * (size_t)tail);
+
+    return pair_list_shrink(list);
+}
+
+
+static inline int
+_pair_list_drop_tail(pair_list_t *list, PyObject *identity, Py_hash_t hash,
+                     Py_ssize_t pos)
+{
+    // return 1 if deleted, 0 if not found
+    pair_t *pair;
+    int ret;
+    int found = 0;
+
+    if (pos >= list->size) {
+        return 0;
+    }
+
+    for (; pos < list->size; pos++) {
+        pair = pair_list_get(list, pos);
+        if (pair->hash != hash) {
+            continue;
+        }
+        ret = str_cmp(pair->identity, identity);
+        if (ret > 0) {
+            if (pair_list_del_at(list, pos) < 0) {
+               return -1;
+            }
+            found = 1;
+            pos--;
+        }
+        else if (ret == -1) {
+            return -1;
+        }
+    }
+
+    return found;
+}
+
+static inline int
+_pair_list_del_hash(pair_list_t *list, PyObject *identity,
+                    PyObject *key, Py_hash_t hash)
+{
+    int ret = _pair_list_drop_tail(list, identity, hash, 0);
+
+    if (ret < 0) {
+        return -1;
+    }
+    else if (ret == 0) {
+        PyErr_SetObject(PyExc_KeyError, key);
+        return -1;
+    }
+    else {
+        list->version = NEXT_VERSION();
+        return 0;
+    }
+}
+
+
+static inline int
+pair_list_del(pair_list_t *list, PyObject *key)
+{
+    PyObject *identity = NULL;
+    Py_hash_t hash;
+    int ret;
+
+    identity = list->calc_identity(key);
+    if (identity == NULL) {
+        goto fail;
+    }
+
+    hash = PyObject_Hash(identity);
+    if (hash == -1) {
+        goto fail;
+    }
+
+    ret = _pair_list_del_hash(list, identity, key, hash);
+    Py_DECREF(identity);
+    return ret;
+fail:
+    Py_XDECREF(identity);
+    return -1;
+}
+
+
+static inline uint64_t
+pair_list_version(pair_list_t *list)
+{
+    return list->version;
+}
+
+
+static inline int
+_pair_list_next(pair_list_t *list, Py_ssize_t *ppos, PyObject **pidentity,
+                PyObject **pkey, PyObject **pvalue, Py_hash_t *phash)
+{
+    pair_t *pair;
+
+    if (*ppos >= list->size) {
+        return 0;
+    }
+
+    pair = pair_list_get(list, *ppos);
+
+    if (pidentity) {
+        *pidentity = pair->identity;
+    }
+    if (pkey) {
+        *pkey = pair->key;
+    }
+    if (pvalue) {
+        *pvalue = pair->value;
+    }
+    if (phash) {
+        *phash = pair->hash;
+    }
+
+    *ppos += 1;
+    return 1;
+}
+
+
+static inline int
+pair_list_next(pair_list_t *list, Py_ssize_t *ppos, PyObject **pidentity,
+               PyObject **pkey, PyObject **pvalue)
+{
+    Py_hash_t hash;
+    return _pair_list_next(list, ppos, pidentity, pkey, pvalue, &hash);
+}
+
+
+static inline int
+pair_list_contains(pair_list_t *list, PyObject *key)
+{
+    Py_hash_t hash1, hash2;
+    Py_ssize_t pos = 0;
+    PyObject *ident = NULL;
+    PyObject *identity = NULL;
+    int tmp;
+
+    ident = list->calc_identity(key);
+    if (ident == NULL) {
+        goto fail;
+    }
+
+    hash1 = PyObject_Hash(ident);
+    if (hash1 == -1) {
+        goto fail;
+    }
+
+    while (_pair_list_next(list, &pos, &identity, NULL, NULL, &hash2)) {
+        if (hash1 != hash2) {
+            continue;
+        }
+        tmp = str_cmp(ident, identity);
+        if (tmp > 0) {
+            Py_DECREF(ident);
+            return 1;
+        }
+        else if (tmp < 0) {
+            goto fail;
+        }
+    }
+
+    Py_DECREF(ident);
+    return 0;
+fail:
+    Py_XDECREF(ident);
+    return -1;
+}
+
+
+static inline PyObject *
+pair_list_get_one(pair_list_t *list, PyObject *key)
+{
+    Py_hash_t hash1, hash2;
+    Py_ssize_t pos = 0;
+    PyObject *ident = NULL;
+    PyObject *identity = NULL;
+    PyObject *value = NULL;
+    int tmp;
+
+    ident = list->calc_identity(key);
+    if (ident == NULL) {
+        goto fail;
+    }
+
+    hash1 = PyObject_Hash(ident);
+    if (hash1 == -1) {
+        goto fail;
+    }
+
+    while (_pair_list_next(list, &pos, &identity, NULL, &value, &hash2)) {
+        if (hash1 != hash2) {
+            continue;
+        }
+        tmp = str_cmp(ident, identity);
+        if (tmp > 0) {
+            Py_INCREF(value);
+            Py_DECREF(ident);
+            return value;
+        }
+        else if (tmp < 0) {
+            goto fail;
+        }
+    }
+
+    Py_DECREF(ident);
+    PyErr_SetObject(PyExc_KeyError, key);
+    return NULL;
+fail:
+    Py_XDECREF(ident);
+    return NULL;
+}
+
+
+static inline PyObject *
+pair_list_get_all(pair_list_t *list, PyObject *key)
+{
+    Py_hash_t hash1, hash2;
+    Py_ssize_t pos = 0;
+    PyObject *ident = NULL;
+    PyObject *identity = NULL;
+    PyObject *value = NULL;
+    PyObject *res = NULL;
+    int tmp;
+
+    ident = list->calc_identity(key);
+    if (ident == NULL) {
+        goto fail;
+    }
+
+    hash1 = PyObject_Hash(ident);
+    if (hash1 == -1) {
+        goto fail;
+    }
+
+    while (_pair_list_next(list, &pos, &identity, NULL, &value, &hash2)) {
+        if (hash1 != hash2) {
+            continue;
+        }
+        tmp = str_cmp(ident, identity);
+        if (tmp > 0) {
+            if (res == NULL) {
+                res = PyList_New(1);
+                if (res == NULL) {
+                    goto fail;
+                }
+                if (PyList_SetItem(res, 0, value) < 0) {
+                    goto fail;
+                }
+                Py_INCREF(value);
+            }
+            else if (PyList_Append(res, value) < 0) {
+                goto fail;
+            }
+        }
+        else if (tmp < 0) {
+            goto fail;
+        }
+    }
+
+    if (res == NULL) {
+        PyErr_SetObject(PyExc_KeyError, key);
+    }
+    Py_DECREF(ident);
+    return res;
+
+fail:
+    Py_XDECREF(ident);
+    Py_XDECREF(res);
+    return NULL;
+}
+
+
+static inline PyObject *
+pair_list_set_default(pair_list_t *list, PyObject *key, PyObject *value)
+{
+    Py_hash_t hash1, hash2;
+    Py_ssize_t pos = 0;
+    PyObject *ident = NULL;
+    PyObject *identity = NULL;
+    PyObject *value2 = NULL;
+    int tmp;
+
+    ident = list->calc_identity(key);
+    if (ident == NULL) {
+        goto fail;
+    }
+
+    hash1 = PyObject_Hash(ident);
+    if (hash1 == -1) {
+        goto fail;
+    }
+
+    while (_pair_list_next(list, &pos, &identity, NULL, &value2, &hash2)) {
+        if (hash1 != hash2) {
+            continue;
+        }
+        tmp = str_cmp(ident, identity);
+        if (tmp > 0) {
+            Py_INCREF(value2);
+            Py_DECREF(ident);
+            return value2;
+        }
+        else if (tmp < 0) {
+            goto fail;
+        }
+    }
+
+    if (_pair_list_add_with_hash(list, ident, key, value, hash1) < 0) {
+        goto fail;
+    }
+
+    Py_INCREF(value);
+    Py_DECREF(ident);
+    return value;
+fail:
+    Py_XDECREF(ident);
+    return NULL;
+}
+
+
+static inline PyObject *
+pair_list_pop_one(pair_list_t *list, PyObject *key)
+{
+    pair_t *pair;
+
+    Py_hash_t hash;
+    Py_ssize_t pos;
+    PyObject *value = NULL;
+    int tmp;
+    PyObject *ident = NULL;
+
+    ident = list->calc_identity(key);
+    if (ident == NULL) {
+        goto fail;
+    }
+
+    hash = PyObject_Hash(ident);
+    if (hash == -1) {
+        goto fail;
+    }
+
+    for (pos=0; pos < list->size; pos++) {
+        pair = pair_list_get(list, pos);
+        if (pair->hash != hash) {
+            continue;
+        }
+        tmp = str_cmp(ident, pair->identity);
+        if (tmp > 0) {
+            value = pair->value;
+            Py_INCREF(value);
+            if (pair_list_del_at(list, pos) < 0) {
+                goto fail;
+            }
+            Py_DECREF(ident);
+            return value;
+        }
+        else if (tmp < 0) {
+            goto fail;
+        }
+    }
+
+    PyErr_SetObject(PyExc_KeyError, key);
+    goto fail;
+
+fail:
+    Py_XDECREF(value);
+    Py_XDECREF(ident);
+    return NULL;
+}
+
+
+static inline PyObject *
+pair_list_pop_all(pair_list_t *list, PyObject *key)
+{
+    Py_hash_t hash;
+    Py_ssize_t pos;
+    pair_t *pair;
+    int tmp;
+    PyObject *res = NULL;
+    PyObject *ident = NULL;
+
+    ident = list->calc_identity(key);
+    if (ident == NULL) {
+        goto fail;
+    }
+
+    hash = PyObject_Hash(ident);
+    if (hash == -1) {
+        goto fail;
+    }
+
+    if (list->size == 0) {
+        PyErr_SetObject(PyExc_KeyError, ident);
+        goto fail;
+    }
+
+    for (pos = list->size - 1; pos >= 0; pos--) {
+        pair = pair_list_get(list, pos);
+        if (hash != pair->hash) {
+            continue;
+        }
+        tmp = str_cmp(ident, pair->identity);
+        if (tmp > 0) {
+            if (res == NULL) {
+                res = PyList_New(1);
+                if (res == NULL) {
+                    goto fail;
+                }
+                if (PyList_SetItem(res, 0, pair->value) < 0) {
+                    goto fail;
+                }
+                Py_INCREF(pair->value);
+            } else if (PyList_Append(res, pair->value) < 0) {
+                goto fail;
+            }
+            if (pair_list_del_at(list, pos) < 0) {
+                goto fail;
+            }
+        }
+        else if (tmp < 0) {
+            goto fail;
+        }
+    }
+
+    if (res == NULL) {
+        PyErr_SetObject(PyExc_KeyError, key);
+    } else if (PyList_Reverse(res) < 0) {
+        goto fail;
+    }
+    Py_DECREF(ident);
+    return res;
+
+fail:
+    Py_XDECREF(ident);
+    Py_XDECREF(res);
+    return NULL;
+}
+
+
+static inline PyObject *
+pair_list_pop_item(pair_list_t *list)
+{
+    PyObject *ret;
+    pair_t *pair;
+
+    if (list->size == 0) {
+        PyErr_SetString(PyExc_KeyError, "empty multidict");
+        return NULL;
+    }
+
+    pair = pair_list_get(list, 0);
+    ret = PyTuple_Pack(2, pair->key, pair->value);
+    if (ret == NULL) {
+        return NULL;
+    }
+
+    if (pair_list_del_at(list, 0) < 0) {
+        Py_DECREF(ret);
+        return NULL;
+    }
+
+    return ret;
+}
+
+
+static inline int
+pair_list_replace(pair_list_t *list, PyObject * key, PyObject *value)
+{
+    pair_t *pair;
+
+    Py_ssize_t pos;
+    int tmp;
+    int found = 0;
+
+    PyObject *identity = NULL;
+    Py_hash_t hash;
+
+    identity = list->calc_identity(key);
+    if (identity == NULL) {
+        goto fail;
+    }
+
+    hash = PyObject_Hash(identity);
+    if (hash == -1) {
+        goto fail;
+    }
+
+
+    for (pos = 0; pos < list->size; pos++) {
+        pair = pair_list_get(list, pos);
+        if (hash != pair->hash) {
+            continue;
+        }
+        tmp = str_cmp(identity, pair->identity);
+        if (tmp > 0) {
+            found = 1;
+            Py_INCREF(key);
+            Py_DECREF(pair->key);
+            pair->key = key;
+            Py_INCREF(value);
+            Py_DECREF(pair->value);
+            pair->value = value;
+            break;
+        }
+        else if (tmp < 0) {
+            goto fail;
+        }
+    }
+
+    if (!found) {
+        if (_pair_list_add_with_hash(list, identity, key, value, hash) < 0) {
+            goto fail;
+        }
+        Py_DECREF(identity);
+        return 0;
+    }
+    else {
+        list->version = NEXT_VERSION();
+        if (_pair_list_drop_tail(list, identity, hash, pos+1) < 0) {
+            goto fail;
+        }
+        Py_DECREF(identity);
+        return 0;
+    }
+fail:
+    Py_XDECREF(identity);
+    return -1;
+}
+
+
+static inline int
+_dict_set_number(PyObject *dict, PyObject *key, Py_ssize_t num)
+{
+    PyObject *tmp = PyLong_FromSsize_t(num);
+    if (tmp == NULL) {
+       return -1;
+    }
+
+    if (PyDict_SetItem(dict, key, tmp) < 0) {
+        Py_DECREF(tmp);
+        return -1;
+    }
+
+    return 0;
+}
+
+
+static inline int
+_pair_list_post_update(pair_list_t *list, PyObject* used_keys, Py_ssize_t pos)
+{
+    pair_t *pair;
+    PyObject *tmp;
+    Py_ssize_t num;
+
+    for (; pos < list->size; pos++) {
+        pair = pair_list_get(list, pos);
+        tmp = PyDict_GetItem(used_keys, pair->identity);
+        if (tmp == NULL) {
+            // not found
+            continue;
+        }
+
+        num = PyLong_AsSsize_t(tmp);
+        if (num == -1) {
+            if (!PyErr_Occurred()) {
+                PyErr_SetString(PyExc_RuntimeError, "invalid internal state");
+            }
+            return -1;
+        }
+
+        if (pos >= num) {
+            // del self[pos]
+            if (pair_list_del_at(list, pos) < 0) {
+                return -1;
+            }
+            pos--;
+        }
+    }
+
+    list->version = NEXT_VERSION();
+    return 0;
+}
+
+// TODO: need refactoring function name
+static inline int
+_pair_list_update(pair_list_t *list, PyObject *key,
+                  PyObject *value, PyObject *used_keys,
+                  PyObject *identity, Py_hash_t hash)
+{
+    PyObject *item = NULL;
+    pair_t *pair = NULL;
+    Py_ssize_t pos;
+    int found;
+    int ident_cmp_res;
+
+    item = PyDict_GetItem(used_keys, identity);
+    if (item == NULL) {
+        pos = 0;
+    }
+    else {
+        pos = PyLong_AsSsize_t(item);
+        if (pos == -1) {
+            if (!PyErr_Occurred()) {
+                PyErr_SetString(PyExc_RuntimeError, "invalid internal state");
+            }
+            return -1;
+        }
+    }
+
+    found = 0;
+    for (; pos < list->size; pos++) {
+        pair = pair_list_get(list, pos);
+        if (pair->hash != hash) {
+            continue;
+        }
+
+        ident_cmp_res = str_cmp(pair->identity, identity);
+        if (ident_cmp_res > 0) {
+            Py_INCREF(key);
+            Py_DECREF(pair->key);
+            pair->key = key;
+
+            Py_INCREF(value);
+            Py_DECREF(pair->value);
+            pair->value = value;
+
+            if (_dict_set_number(used_keys, pair->identity, pos + 1) < 0) {
+                return -1;
+            }
+
+            found = 1;
+            break;
+        }
+        else if (ident_cmp_res < 0) {
+            return -1;
+        }
+    }
+
+    if (!found) {
+        if (_pair_list_add_with_hash(list, identity, key, value, hash) < 0) {
+            return -1;
+        }
+        if (_dict_set_number(used_keys, identity, list->size) < 0) {
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
+
+static inline int
+pair_list_update(pair_list_t *list, pair_list_t *other)
+{
+    PyObject *used_keys = NULL;
+    pair_t *pair = NULL;
+
+    Py_ssize_t pos;
+
+    if (other->size == 0) {
+        return 0;
+    }
+
+    used_keys = PyDict_New();
+    if (used_keys == NULL) {
+        return -1;
+    }
+
+    for (pos = 0; pos < other->size; pos++) {
+        pair = pair_list_get(other, pos);
+        if (_pair_list_update(list, pair->key, pair->value, used_keys,
+                              pair->identity, pair->hash) < 0) {
+            goto fail;
+        }
+    }
+
+    if (_pair_list_post_update(list, used_keys, 0) < 0) {
+        goto fail;
+    }
+
+    Py_DECREF(used_keys);
+    return 0;
+
+fail:
+    Py_XDECREF(used_keys);
+    return -1;
+}
+
+
+static inline int
+pair_list_update_from_seq(pair_list_t *list, PyObject *seq)
+{
+    PyObject *it = NULL; // iter(seq)
+    PyObject *fast = NULL; // item as a 2-tuple or 2-list
+    PyObject *item = NULL; // seq[i]
+    PyObject *used_keys = NULL; // dict(<Identitty: Pos>)
+
+    PyObject *key = NULL;
+    PyObject *value = NULL;
+    PyObject *identity = NULL;
+
+    Py_hash_t hash;
+
+    Py_ssize_t i;
+    Py_ssize_t n;
+
+    it = PyObject_GetIter(seq);
+    if (it == NULL) {
+        return -1;
+    }
+
+    used_keys = PyDict_New();
+    if (used_keys == NULL) {
+        goto fail_1;
+    }
+
+    for (i = 0; ; ++i) { // i - index into seq of current element
+        fast = NULL;
+        item = PyIter_Next(it);
+        if (item == NULL) {
+            if (PyErr_Occurred()) {
+                goto fail_1;
+            }
+            break;
+        }
+
+        // Convert item to sequence, and verify length 2.
+        fast = PySequence_Fast(item, "");
+        if (fast == NULL) {
+            if (PyErr_ExceptionMatches(PyExc_TypeError)) {
+                PyErr_Format(PyExc_TypeError,
+                             "multidict cannot convert sequence element #%zd"
+                             " to a sequence",
+                             i);
+            }
+            goto fail_1;
+        }
+
+        n = PySequence_Fast_GET_SIZE(fast);
+        if (n != 2) {
+            PyErr_Format(PyExc_ValueError,
+                         "multidict update sequence element #%zd "
+                         "has length %zd; 2 is required",
+                         i, n);
+            goto fail_1;
+        }
+
+        key = PySequence_Fast_GET_ITEM(fast, 0);
+        value = PySequence_Fast_GET_ITEM(fast, 1);
+        Py_INCREF(key);
+        Py_INCREF(value);
+
+        identity = list->calc_identity(key);
+        if (identity == NULL) {
+            goto fail_1;
+        }
+
+        hash = PyObject_Hash(identity);
+        if (hash == -1) {
+            goto fail_1;
+        }
+
+        if (_pair_list_update(list, key, value, used_keys, identity, hash) < 0) {
+            goto fail_1;
+        }
+
+        Py_DECREF(key);
+        Py_DECREF(value);
+        Py_DECREF(fast);
+        Py_DECREF(item);
+        Py_DECREF(identity);
+    }
+
+    if (_pair_list_post_update(list, used_keys, 0) < 0) {
+        goto fail_2;
+    }
+
+    Py_DECREF(it);
+    Py_DECREF(used_keys);
+    return 0;
+
+fail_1:
+    Py_XDECREF(key);
+    Py_XDECREF(value);
+    Py_XDECREF(fast);
+    Py_XDECREF(item);
+    Py_XDECREF(identity);
+
+fail_2:
+    Py_XDECREF(it);
+    Py_XDECREF(used_keys);
+    return -1;
+}
+
+static inline int
+pair_list_eq_to_mapping(pair_list_t *list, PyObject *other)
+{
+    PyObject *key = NULL;
+    PyObject *avalue = NULL;
+    PyObject *bvalue;
+
+    Py_ssize_t pos, other_len;
+
+    int eq;
+
+    if (!PyMapping_Check(other)) {
+        PyErr_Format(PyExc_TypeError,
+                     "other argument must be a mapping, not %s",
+                     Py_TYPE(other)->tp_name);
+        return -1;
+    }
+
+    other_len = PyMapping_Size(other);
+    if (other_len < 0) {
+        return -1;
+    }
+    if (pair_list_len(list) != other_len) {
+        return 0;
+    }
+
+    pos = 0;
+    while (pair_list_next(list, &pos, NULL, &key, &avalue)) {
+        bvalue = PyObject_GetItem(other, key);
+        if (bvalue == NULL) {
+            if (PyErr_ExceptionMatches(PyExc_KeyError)) {
+                PyErr_Clear();
+                return 0;
+            }
+            return -1;
+        }
+
+        eq = PyObject_RichCompareBool(avalue, bvalue, Py_EQ);
+        Py_DECREF(bvalue);
+
+        if (eq <= 0) {
+            return eq;
+        }
+    }
+
+    return 1;
+}
+
+
+/***********************************************************************/
+
+static inline int
+pair_list_traverse(pair_list_t *list, visitproc visit, void *arg)
+{
+    pair_t *pair = NULL;
+    Py_ssize_t pos;
+
+    for (pos = 0; pos < list->size; pos++) {
+        pair = pair_list_get(list, pos);
+        // Don't need traverse the identity: it is a terminal
+        Py_VISIT(pair->key);
+        Py_VISIT(pair->value);
+    }
+
+    return 0;
+}
+
+
+static inline int
+pair_list_clear(pair_list_t *list)
+{
+    pair_t *pair = NULL;
+    Py_ssize_t pos;
+
+    if (list->size == 0) {
+        return 0;
+    }
+
+    list->version = NEXT_VERSION();
+    for (pos = 0; pos < list->size; pos++) {
+        pair = pair_list_get(list, pos);
+        Py_CLEAR(pair->key);
+        Py_CLEAR(pair->identity);
+        Py_CLEAR(pair->value);
+    }
+    list->size = 0;
+    if (list->pairs != list->buffer) {
+        PyMem_Del(list->pairs);
+        list->pairs = list->buffer;
+    }
+
+    return 0;
+}
+
+
+#ifdef __cplusplus
+}
+#endif
+#endif
diff --git a/third_party/python/multidict/multidict/_multilib/views.h b/third_party/python/multidict/multidict/_multilib/views.h
new file mode 100644
index 0000000000..5b1ebfe77c
--- /dev/null
+++ b/third_party/python/multidict/multidict/_multilib/views.h
@@ -0,0 +1,464 @@
+#ifndef _MULTIDICT_VIEWS_H
+#define _MULTIDICT_VIEWS_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+static PyTypeObject multidict_itemsview_type;
+static PyTypeObject multidict_valuesview_type;
+static PyTypeObject multidict_keysview_type;
+
+static PyObject *viewbaseset_richcmp_func;
+static PyObject *viewbaseset_and_func;
+static PyObject *viewbaseset_or_func;
+static PyObject *viewbaseset_sub_func;
+static PyObject *viewbaseset_xor_func;
+
+static PyObject *abc_itemsview_register_func;
+static PyObject *abc_keysview_register_func;
+static PyObject *abc_valuesview_register_func;
+
+static PyObject *itemsview_isdisjoint_func;
+static PyObject *itemsview_repr_func;
+
+static PyObject *keysview_repr_func;
+static PyObject *keysview_isdisjoint_func;
+
+static PyObject *valuesview_repr_func;
+
+typedef struct {
+    PyObject_HEAD
+    PyObject *md;
+} _Multidict_ViewObject;
+
+
+/********** Base **********/
+
+static inline void
+_init_view(_Multidict_ViewObject *self, PyObject *md)
+{
+    Py_INCREF(md);
+    self->md = md;
+}
+
+static inline void
+multidict_view_dealloc(_Multidict_ViewObject *self)
+{
+    PyObject_GC_UnTrack(self);
+    Py_XDECREF(self->md);
+    PyObject_GC_Del(self);
+}
+
+static inline int
+multidict_view_traverse(_Multidict_ViewObject *self, visitproc visit, void *arg)
+{
+    Py_VISIT(self->md);
+    return 0;
+}
+
+static inline int
+multidict_view_clear(_Multidict_ViewObject *self)
+{
+    Py_CLEAR(self->md);
+    return 0;
+}
+
+static inline Py_ssize_t
+multidict_view_len(_Multidict_ViewObject *self)
+{
+    return pair_list_len(&((MultiDictObject*)self->md)->pairs);
+}
+
+static inline PyObject *
+multidict_view_richcompare(PyObject *self, PyObject *other, int op)
+{
+    PyObject *ret;
+    PyObject *op_obj = PyLong_FromLong(op);
+    if (op_obj == NULL) {
+        return NULL;
+    }
+    ret = PyObject_CallFunctionObjArgs(
+        viewbaseset_richcmp_func, self, other, op_obj, NULL);
+    Py_DECREF(op_obj);
+    return ret;
+}
+
+static inline PyObject *
+multidict_view_and(PyObject *self, PyObject *other)
+{
+    return PyObject_CallFunctionObjArgs(
+        viewbaseset_and_func, self, other, NULL);
+}
+
+static inline PyObject *
+multidict_view_or(PyObject *self, PyObject *other)
+{
+    return PyObject_CallFunctionObjArgs(
+        viewbaseset_or_func, self, other, NULL);
+}
+
+static inline PyObject *
+multidict_view_sub(PyObject *self, PyObject *other)
+{
+    return PyObject_CallFunctionObjArgs(
+        viewbaseset_sub_func, self, other, NULL);
+}
+
+static inline PyObject *
+multidict_view_xor(PyObject *self, PyObject *other)
+{
+    return PyObject_CallFunctionObjArgs(
+        viewbaseset_xor_func, self, other, NULL);
+}
+
+static PyNumberMethods multidict_view_as_number = {
+    .nb_subtract = (binaryfunc)multidict_view_sub,
+    .nb_and = (binaryfunc)multidict_view_and,
+    .nb_xor = (binaryfunc)multidict_view_xor,
+    .nb_or = (binaryfunc)multidict_view_or,
+};
+
+/********** Items **********/
+
+static inline PyObject *
+multidict_itemsview_new(PyObject *md)
+{
+    _Multidict_ViewObject *mv = PyObject_GC_New(
+        _Multidict_ViewObject, &multidict_itemsview_type);
+    if (mv == NULL) {
+        return NULL;
+    }
+
+    _init_view(mv, md);
+
+    PyObject_GC_Track(mv);
+    return (PyObject *)mv;
+}
+
+static inline PyObject *
+multidict_itemsview_iter(_Multidict_ViewObject *self)
+{
+    return multidict_items_iter_new((MultiDictObject*)self->md);
+}
+
+static inline PyObject *
+multidict_itemsview_repr(_Multidict_ViewObject *self)
+{
+    return PyObject_CallFunctionObjArgs(
+        itemsview_repr_func, self, NULL);
+}
+
+static inline PyObject *
+multidict_itemsview_isdisjoint(_Multidict_ViewObject *self, PyObject *other)
+{
+    return PyObject_CallFunctionObjArgs(
+        itemsview_isdisjoint_func, self, other, NULL);
+}
+
+PyDoc_STRVAR(itemsview_isdisjoint_doc,
+             "Return True if two sets have a null intersection.");
+
+static PyMethodDef multidict_itemsview_methods[] = {
+    {
+        "isdisjoint",
+        (PyCFunction)multidict_itemsview_isdisjoint,
+        METH_O,
+        itemsview_isdisjoint_doc
+    },
+    {
+        NULL,
+        NULL
+    }   /* sentinel */
+};
+
+static inline int
+multidict_itemsview_contains(_Multidict_ViewObject *self, PyObject *obj)
+{
+    PyObject *akey  = NULL,
+             *aval  = NULL,
+             *bkey  = NULL,
+             *bval  = NULL,
+             *iter  = NULL,
+             *item  = NULL;
+    int ret1, ret2;
+
+    if (!PyTuple_Check(obj) || PyTuple_GET_SIZE(obj) != 2) {
+        return 0;
+    }
+
+    bkey = PyTuple_GET_ITEM(obj, 0);
+    bval = PyTuple_GET_ITEM(obj, 1);
+
+    iter = multidict_itemsview_iter(self);
+    if (iter == NULL) {
+        return 0;
+    }
+
+    while ((item = PyIter_Next(iter)) != NULL) {
+        akey = PyTuple_GET_ITEM(item, 0);
+        aval = PyTuple_GET_ITEM(item, 1);
+
+        ret1 = PyObject_RichCompareBool(akey, bkey, Py_EQ);
+        if (ret1 < 0) {
+            Py_DECREF(iter);
+            Py_DECREF(item);
+            return -1;
+        }
+        ret2 = PyObject_RichCompareBool(aval, bval, Py_EQ);
+        if (ret2 < 0) {
+            Py_DECREF(iter);
+            Py_DECREF(item);
+            return -1;
+        }
+        if (ret1 > 0 && ret2 > 0)
+        {
+            Py_DECREF(iter);
+            Py_DECREF(item);
+            return 1;
+        }
+
+        Py_DECREF(item);
+    }
+
+    Py_DECREF(iter);
+
+    if (PyErr_Occurred()) {
+        return -1;
+    }
+
+    return 0;
+}
+
+static PySequenceMethods multidict_itemsview_as_sequence = {
+    .sq_length = (lenfunc)multidict_view_len,
+    .sq_contains = (objobjproc)multidict_itemsview_contains,
+};
+
+static PyTypeObject multidict_itemsview_type = {
+    PyVarObject_HEAD_INIT(DEFERRED_ADDRESS(&PyType_Type), 0)
+    "multidict._multidict._ItemsView",              /* tp_name */
+    sizeof(_Multidict_ViewObject),                  /* tp_basicsize */
+    .tp_dealloc = (destructor)multidict_view_dealloc,
+    .tp_repr = (reprfunc)multidict_itemsview_repr,
+    .tp_as_number = &multidict_view_as_number,
+    .tp_as_sequence = &multidict_itemsview_as_sequence,
+    .tp_getattro = PyObject_GenericGetAttr,
+    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,
+    .tp_traverse = (traverseproc)multidict_view_traverse,
+    .tp_clear = (inquiry)multidict_view_clear,
+    .tp_richcompare = multidict_view_richcompare,
+    .tp_iter = (getiterfunc)multidict_itemsview_iter,
+    .tp_methods = multidict_itemsview_methods,
+};
+
+
+/********** Keys **********/
+
+static inline PyObject *
+multidict_keysview_new(PyObject *md)
+{
+    _Multidict_ViewObject *mv = PyObject_GC_New(
+        _Multidict_ViewObject, &multidict_keysview_type);
+    if (mv == NULL) {
+        return NULL;
+    }
+
+    _init_view(mv, md);
+
+    PyObject_GC_Track(mv);
+    return (PyObject *)mv;
+}
+
+static inline PyObject *
+multidict_keysview_iter(_Multidict_ViewObject *self)
+{
+    return multidict_keys_iter_new(((MultiDictObject*)self->md));
+}
+
+static inline PyObject *
+multidict_keysview_repr(_Multidict_ViewObject *self)
+{
+    return PyObject_CallFunctionObjArgs(
+        keysview_repr_func, self, NULL);
+}
+
+static inline PyObject *
+multidict_keysview_isdisjoint(_Multidict_ViewObject *self, PyObject *other)
+{
+    return PyObject_CallFunctionObjArgs(
+        keysview_isdisjoint_func, self, other, NULL);
+}
+
+PyDoc_STRVAR(keysview_isdisjoint_doc,
+             "Return True if two sets have a null intersection.");
+
+static PyMethodDef multidict_keysview_methods[] = {
+    {
+        "isdisjoint",
+        (PyCFunction)multidict_keysview_isdisjoint,
+        METH_O,
+        keysview_isdisjoint_doc
+    },
+    {
+        NULL,
+        NULL
+    }   /* sentinel */
+};
+
+static inline int
+multidict_keysview_contains(_Multidict_ViewObject *self, PyObject *key)
+{
+    return pair_list_contains(&((MultiDictObject*)self->md)->pairs, key);
+}
+
+static PySequenceMethods multidict_keysview_as_sequence = {
+    .sq_length = (lenfunc)multidict_view_len,
+    .sq_contains = (objobjproc)multidict_keysview_contains,
+};
+
+static PyTypeObject multidict_keysview_type = {
+    PyVarObject_HEAD_INIT(DEFERRED_ADDRESS(&PyType_Type), 0)
+    "multidict._multidict._KeysView",              /* tp_name */
+    sizeof(_Multidict_ViewObject),                 /* tp_basicsize */
+    .tp_dealloc = (destructor)multidict_view_dealloc,
+    .tp_repr = (reprfunc)multidict_keysview_repr,
+    .tp_as_number = &multidict_view_as_number,
+    .tp_as_sequence = &multidict_keysview_as_sequence,
+    .tp_getattro = PyObject_GenericGetAttr,
+    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,
+    .tp_traverse = (traverseproc)multidict_view_traverse,
+    .tp_clear = (inquiry)multidict_view_clear,
+    .tp_richcompare = multidict_view_richcompare,
+    .tp_iter = (getiterfunc)multidict_keysview_iter,
+    .tp_methods = multidict_keysview_methods,
+};
+
+
+/********** Values **********/
+
+static inline PyObject *
+multidict_valuesview_new(PyObject *md)
+{
+    _Multidict_ViewObject *mv = PyObject_GC_New(
+        _Multidict_ViewObject, &multidict_valuesview_type);
+    if (mv == NULL) {
+        return NULL;
+    }
+
+    _init_view(mv, md);
+
+    PyObject_GC_Track(mv);
+    return (PyObject *)mv;
+}
+
+static inline PyObject *
+multidict_valuesview_iter(_Multidict_ViewObject *self)
+{
+    return multidict_values_iter_new(((MultiDictObject*)self->md));
+}
+
+static inline PyObject *
+multidict_valuesview_repr(_Multidict_ViewObject *self)
+{
+    return PyObject_CallFunctionObjArgs(
+        valuesview_repr_func, self, NULL);
+}
+
+static PySequenceMethods multidict_valuesview_as_sequence = {
+    .sq_length = (lenfunc)multidict_view_len,
+};
+
+static PyTypeObject multidict_valuesview_type = {
+    PyVarObject_HEAD_INIT(DEFERRED_ADDRESS(&PyType_Type), 0)
+    "multidict._multidict._ValuesView",              /* tp_name */
+    sizeof(_Multidict_ViewObject),                   /* tp_basicsize */
+    .tp_dealloc = (destructor)multidict_view_dealloc,
+    .tp_repr = (reprfunc)multidict_valuesview_repr,
+    .tp_as_sequence = &multidict_valuesview_as_sequence,
+    .tp_getattro = PyObject_GenericGetAttr,
+    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,
+    .tp_traverse = (traverseproc)multidict_view_traverse,
+    .tp_clear = (inquiry)multidict_view_clear,
+    .tp_iter = (getiterfunc)multidict_valuesview_iter,
+};
+
+
+static inline int
+multidict_views_init()
+{
+    PyObject *reg_func_call_result = NULL;
+    PyObject *module = PyImport_ImportModule("multidict._multidict_base");
+    if (module == NULL) {
+        goto fail;
+    }
+
+#define GET_MOD_ATTR(VAR, NAME)                 \
+    VAR = PyObject_GetAttrString(module, NAME); \
+    if (VAR == NULL) {                          \
+        goto fail;                              \
+    }
+
+    GET_MOD_ATTR(viewbaseset_richcmp_func, "_viewbaseset_richcmp");
+    GET_MOD_ATTR(viewbaseset_and_func, "_viewbaseset_and");
+    GET_MOD_ATTR(viewbaseset_or_func, "_viewbaseset_or");
+    GET_MOD_ATTR(viewbaseset_sub_func, "_viewbaseset_sub");
+    GET_MOD_ATTR(viewbaseset_xor_func, "_viewbaseset_xor");
+
+    GET_MOD_ATTR(abc_itemsview_register_func, "_abc_itemsview_register");
+    GET_MOD_ATTR(abc_keysview_register_func, "_abc_keysview_register");
+    GET_MOD_ATTR(abc_valuesview_register_func, "_abc_valuesview_register");
+
+    GET_MOD_ATTR(itemsview_repr_func, "_itemsview_isdisjoint");
+    GET_MOD_ATTR(itemsview_repr_func, "_itemsview_repr");
+
+    GET_MOD_ATTR(keysview_repr_func, "_keysview_repr");
+    GET_MOD_ATTR(keysview_isdisjoint_func, "_keysview_isdisjoint");
+
+    GET_MOD_ATTR(valuesview_repr_func, "_valuesview_repr");
+
+    if (PyType_Ready(&multidict_itemsview_type) < 0 ||
+        PyType_Ready(&multidict_valuesview_type) < 0 ||
+        PyType_Ready(&multidict_keysview_type) < 0)
+    {
+        goto fail;
+    }
+
+    // abc.ItemsView.register(_ItemsView)
+    reg_func_call_result = PyObject_CallFunctionObjArgs(
+        abc_itemsview_register_func, (PyObject*)&multidict_itemsview_type, NULL);
+    if (reg_func_call_result == NULL) {
+        goto fail;
+    }
+    Py_DECREF(reg_func_call_result);
+
+    // abc.KeysView.register(_KeysView)
+    reg_func_call_result = PyObject_CallFunctionObjArgs(
+        abc_keysview_register_func, (PyObject*)&multidict_keysview_type, NULL);
+    if (reg_func_call_result == NULL) {
+        goto fail;
+    }
+    Py_DECREF(reg_func_call_result);
+
+    // abc.ValuesView.register(_KeysView)
+    reg_func_call_result = PyObject_CallFunctionObjArgs(
+        abc_valuesview_register_func, (PyObject*)&multidict_valuesview_type, NULL);
+    if (reg_func_call_result == NULL) {
+        goto fail;
+    }
+    Py_DECREF(reg_func_call_result);
+
+    Py_DECREF(module);
+    return 0;
+
+fail:
+    Py_CLEAR(module);
+    return -1;
+
+#undef GET_MOD_ATTR
+}
+
+#ifdef __cplusplus
+}
+#endif
+#endif
diff --git a/third_party/python/multidict/multidict/py.typed b/third_party/python/multidict/multidict/py.typed
new file mode 100644
index 0000000000..dfe8cc048e
--- /dev/null
+++ b/third_party/python/multidict/multidict/py.typed
@@ -0,0 +1 @@
+PEP-561 marker.
\ No newline at end of file
diff --git a/third_party/python/multidict/pyproject.toml b/third_party/python/multidict/pyproject.toml
new file mode 100644
index 0000000000..f1b83b8f62
--- /dev/null
+++ b/third_party/python/multidict/pyproject.toml
@@ -0,0 +1,11 @@
+[build-system]
+requires = ["setuptools>=40", "wheel"]
+
+
+[tool.towncrier]
+package = "multidict"
+filename = "CHANGES.rst"
+directory = "CHANGES/"
+title_format = "{version} ({project_date})"
+template = "CHANGES/.TEMPLATE.rst"
+issue_format = "`#{issue} <https://github.com/aio-libs/multidict/issues/{issue}>`_"
diff --git a/third_party/python/multidict/setup.cfg b/third_party/python/multidict/setup.cfg
new file mode 100644
index 0000000000..2c11fd4aed
--- /dev/null
+++ b/third_party/python/multidict/setup.cfg
@@ -0,0 +1,37 @@
+[aliases]
+test = pytest
+
+[metadata]
+license_files = 
+	LICENSE
+long_description = file: README.rst
+
+[flake8]
+ignore = E302,E701,E305,E704,F811,N811, W503
+max-line-length = 88
+
+[isort]
+multi_line_output = 3
+include_trailing_comma = True
+force_grid_wrap = 0
+use_parentheses = True
+known_first_party = multidict
+known_third_party = pytest
+
+[tool:pytest]
+testpaths = tests
+norecursedirs = dist build .tox docs requirements tools
+addopts = --doctest-modules --cov=multidict --cov-report term-missing:skip-covered --cov-report xml --junitxml=junit-test-results.xml -v
+doctest_optionflags = ALLOW_UNICODE ELLIPSIS
+junit_family = xunit2
+
+[mypy-pytest]
+ignore_missing_imports = true
+
+[mypy-multidict._multidict]
+ignore_missing_imports = true
+
+[egg_info]
+tag_build = 
+tag_date = 0
+
diff --git a/third_party/python/multidict/setup.py b/third_party/python/multidict/setup.py
new file mode 100644
index 0000000000..044f1d72ed
--- /dev/null
+++ b/third_party/python/multidict/setup.py
@@ -0,0 +1,96 @@
+import codecs
+import os
+import platform
+import re
+import sys
+
+from setuptools import Extension, setup
+
+NO_EXTENSIONS = bool(os.environ.get("MULTIDICT_NO_EXTENSIONS"))
+
+if sys.implementation.name != "cpython":
+    NO_EXTENSIONS = True
+
+CFLAGS = ["-O2"]
+# CFLAGS = ['-g']
+if platform.system() != "Windows":
+    CFLAGS.extend(
+        [
+            "-std=c99",
+            "-Wall",
+            "-Wsign-compare",
+            "-Wconversion",
+            "-fno-strict-aliasing",
+            "-pedantic",
+        ]
+    )
+
+extensions = [
+    Extension(
+        "multidict._multidict",
+        ["multidict/_multidict.c"],
+        extra_compile_args=CFLAGS,
+    ),
+]
+
+
+with codecs.open(
+    os.path.join(
+        os.path.abspath(os.path.dirname(__file__)), "multidict", "__init__.py"
+    ),
+    "r",
+    "latin1",
+) as fp:
+    try:
+        version = re.findall(r'^__version__ = "([^"]+)"\r?$', fp.read(), re.M)[0]
+    except IndexError:
+        raise RuntimeError("Unable to determine version.")
+
+
+def read(f):
+    return open(os.path.join(os.path.dirname(__file__), f)).read().strip()
+
+
+args = dict(
+    name="multidict",
+    version=version,
+    description=("multidict implementation"),
+    long_description=read("README.rst"),
+    classifiers=[
+        "License :: OSI Approved :: Apache Software License",
+        "Intended Audience :: Developers",
+        "Programming Language :: Python",
+        "Programming Language :: Python :: 3",
+        "Programming Language :: Python :: 3.6",
+        "Programming Language :: Python :: 3.7",
+        "Programming Language :: Python :: 3.8",
+        "Programming Language :: Python :: 3.9",
+        "Development Status :: 5 - Production/Stable",
+    ],
+    author="Andrew Svetlov",
+    author_email="andrew.svetlov@gmail.com",
+    url="https://github.com/aio-libs/multidict",
+    project_urls={
+        "Chat: Gitter": "https://gitter.im/aio-libs/Lobby",
+        "CI: Azure Pipelines": "https://dev.azure.com/aio-libs/multidict/_build",
+        "Coverage: codecov": "https://codecov.io/github/aio-libs/multidict",
+        "Docs: RTD": "https://multidict.readthedocs.io",
+        "GitHub: issues": "https://github.com/aio-libs/multidict/issues",
+        "GitHub: repo": "https://github.com/aio-libs/multidict",
+    },
+    license="Apache 2",
+    packages=["multidict"],
+    python_requires=">=3.6",
+    include_package_data=True,
+)
+
+if not NO_EXTENSIONS:
+    print("*********************")
+    print("* Accelerated build *")
+    print("*********************")
+    setup(ext_modules=extensions, **args)
+else:
+    print("*********************")
+    print("* Pure Python build *")
+    print("*********************")
+    setup(**args)