Adding upstream version 2.2.1.

Signed-off-by: Daniel Baumann <daniel@debian.org>

staslib/singleton.py

@@ -0,0 +1,23 @@
+# 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]