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+# Copyright (c) 2022, Dell Inc. or its subsidiaries. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+# See the LICENSE file for details.
+#
+# This file is part of NVMe STorage Appliance Services (nvme-stas).
+#
+# Authors: Martin Belanger <Martin.Belanger@dell.com>
+#
+'''Implementation of a singleton pattern'''
+
+
+class Singleton(type):
+ '''metaclass implementation of a singleton pattern'''
+
+ _instances = {}
+
+ def __call__(cls, *args, **kwargs):
+ if cls not in cls._instances:
+ # This variable declaration is required to force a
+ # strong reference on the instance.
+ instance = super(Singleton, cls).__call__(*args, **kwargs)
+ cls._instances[cls] = instance
+ return cls._instances[cls]