code: def Add(self, request, callback=None):
          
          handler = RequestResponseAndHandler(request, None, callback)
          self.__request_response_handlers[self._NewId()] = handler
docs: Add a new request.
  
          Args:
            request: A http_wrapper.Request to add to the batch.
            callback: A callback to be called for this response, of the
                form callback(response, exception). The first parameter is the
                deserialized response object. The second is an
                apiclient.errors.HttpError exception object if an HTTP error
                occurred while processing the request, or None if no errors
                occurred.
  
          Returns:
            None