fix(generator): address PR review comments in _compat.py.j2

Author: hebaalazzeh

packages/gapic-generator/gapic/templates/%namespace/%name_%version/%sub/_compat.py.j2

@@ -1,12 +1,15 @@
 # {% include '_license.j2' %}
 
+"""A fallback module for `google.api_core.gapic_v1.request` for backward compatibility.
+"""
+
 import uuid
 
 try:
     from google.api_core.gapic_v1.request import setup_request_id  # type: ignore
-except ImportError:  # pragma: NO COVER
+except ImportError:
     # TODO(https://github.com/googleapis/google-cloud-python/issues/17813): Remove this fallback when google-api-core >= 2.26.0 is the minimum required version.
-    def setup_request_id(request, field_name: str, is_proto3_optional: bool):  # pragma: NO COVER
+    def setup_request_id(request, field_name: str, is_proto3_optional: bool):
         """Populate a UUID4 field in the request if it is not already set.
 
         Args: