fix: make timeout an optional positional arg [(#3938)](GoogleCloudPla…

…tform/python-docs-samples#3938)

* fix: make timeout an optional positional arg

* place `none` back in function signature

Co-authored-by: Bu Sun Kim <8822365+busunkim96@users.noreply.github.com>

samples/snippets/subscriber.py

@@ -678,22 +678,24 @@ def callback(message):
 
     receive_parser = subparsers.add_parser("receive", help=receive_messages.__doc__)
     receive_parser.add_argument("subscription_name")
-    receive_parser.add_argument("--timeout", default=None, type=float)
+    receive_parser.add_argument("timeout", default=None, type=float, nargs="?")
 
     receive_with_custom_attributes_parser = subparsers.add_parser(
         "receive-custom-attributes",
         help=receive_messages_with_custom_attributes.__doc__,
     )
     receive_with_custom_attributes_parser.add_argument("subscription_name")
     receive_with_custom_attributes_parser.add_argument(
-        "--timeout", default=None, type=float
+        "timeout", default=None, type=float, nargs="?"
     )
 
     receive_with_flow_control_parser = subparsers.add_parser(
         "receive-flow-control", help=receive_messages_with_flow_control.__doc__
     )
     receive_with_flow_control_parser.add_argument("subscription_name")
-    receive_with_flow_control_parser.add_argument("--timeout", default=None, type=float)
+    receive_with_flow_control_parser.add_argument(
+        "timeout", default=None, type=float, nargs="?"
+    )
 
     synchronous_pull_parser = subparsers.add_parser(
         "receive-synchronously", help=synchronous_pull.__doc__
@@ -710,15 +712,17 @@ def callback(message):
         "listen-for-errors", help=listen_for_errors.__doc__
     )
     listen_for_errors_parser.add_argument("subscription_name")
-    listen_for_errors_parser.add_argument("--timeout", default=None, type=float)
+    listen_for_errors_parser.add_argument(
+        "timeout", default=None, type=float, nargs="?"
+    )
 
     receive_messages_with_delivery_attempts_parser = subparsers.add_parser(
         "receive-messages-with-delivery-attempts",
         help=receive_messages_with_delivery_attempts.__doc__,
     )
     receive_messages_with_delivery_attempts_parser.add_argument("subscription_name")
     receive_messages_with_delivery_attempts_parser.add_argument(
-        "--timeout", default=None, type=float
+        "timeout", default=None, type=float, nargs="?"
     )
 
     args = parser.parse_args()