Autogenerated snippets are incorrect when field type is a list

[Ark-kun]

Example:

https://github.com/googleapis/python-aiplatform/blob/3d468ed10629e3d0f211f413af054e21620e5952/google/cloud/aiplatform_v1beta1/services/prediction_service/client.py#L1079

Proto:

message CountTokensRequest {
  string endpoint = 1;
  repeated google.protobuf.Value instances = 2;
}

Generated snippet and correction:

            from google.cloud import aiplatform_v1beta1

            def sample_count_tokens():
                # Create a client
                client = aiplatform_v1beta1.PredictionServiceClient()

                # Initialize request argument(s)
-                instances = aiplatform_v1beta1.Value()
-                instances.null_value = "NULL_VALUE"
+                instances_0 = aiplatform_v1beta1.Value()
+                instances_0.null_value = "NULL_VALUE"

                request = aiplatform_v1beta1.CountTokensRequest(
                    endpoint="endpoint_value",
-                    instances=instances,
+                    instances=[instances_0],
                )

                # Make the request
                response = client.count_tokens(request=request)

                # Handle the response
                print(response)