docs: def _handle_cancel_notification(self, msg_id):
          """Handle a cancel notification from the client."""
          request_future = self._client_request_futures.pop(msg_id, None)
  
          if not request_future:
              log.warn("Received cancel notification for unknown message id %s", msg_id)
              return
  
          # Will only work if the request hasn't started executing
          if request_future.cancel():
              log.debug("Cancelled request with id %s", msg_id)