Introduced metrics to opensearch-py client

Signed-off-by: saimedhi <[email protected]>

opensearchpy/metrics.py

@@ -1,3 +1,12 @@
+# SPDX-License-Identifier: Apache-2.0
+#
+# The OpenSearch Contributors require contributions made to
+# this file be licensed under the Apache-2.0 license or a
+# compatible open source license.
+#
+# Modifications Copyright OpenSearch Contributors. See
+# GitHub history for details.
+
 import time
 from abc import ABC, abstractmethod
 
@@ -53,4 +62,4 @@ def request_end(self) -> None:
 
     def _on_request_end(self) -> None:
         self._end_time = time.perf_counter()
-        self._service_time = self._end_time - self._start_time
+        self._service_time = self._end_time - self._start_time