import os def handle_headers(frame, request, response): resource_url = request.GET.first(b"resource-url").decode() link_header_value = "<{}>; rel=preload; as=image".format(resource_url) early_hints = [ (b":status", b"103"), (b"link", link_header_value), ] response.writer.write_raw_header_frame(headers=early_hints, end_headers=True) response.status = 404 response.headers[b"content-type"] = "text/html" response.write_status_headers() def main(request, response): current_dir = os.path.dirname(os.path.realpath(__file__)) file_path = os.path.join(current_dir, "404-with-early-hints.html") with open(file_path, "r") as f: test_content = f.read() response.writer.write_data(item=test_content, last=True)