docs(documentai): add 2.7 deprecation warning (via synth) (#10041)

Author: yoshi-automation

documentai/google/cloud/documentai_v1beta1/__init__.py

@@ -16,12 +16,23 @@
 
 
 from __future__ import absolute_import
+import sys
+import warnings
 
 from google.cloud.documentai_v1beta1 import types
 from google.cloud.documentai_v1beta1.gapic import document_understanding_service_client
 from google.cloud.documentai_v1beta1.gapic import enums
 
 
+if sys.version_info[:2] == (2, 7):
+    message = (
+        "A future version of this library will drop support for Python 2.7."
+        "More details about Python 2 support for Google Cloud Client Libraries"
+        "can be found at https://cloud.google.com/python/docs/python2-sunset/"
+    )
+    warnings.warn(message, DeprecationWarning)
+
+
 class DocumentUnderstandingServiceClient(
     document_understanding_service_client.DocumentUnderstandingServiceClient
 ):