code: def send_buffered_messages(self):
      
      while not self.out_stream.is_empty() and self._stmgr_client.is_registered:
        tuple_set = self.out_stream.poll()
        if isinstance(tuple_set, tuple_pb2.HeronTupleSet):
          tuple_set.src_task_id = self.my_pplan_helper.my_task_id
          self.gateway_metrics.update_sent_packet(tuple_set.ByteSize())
        self._stmgr_client.send_message(tuple_set)
docs: Send messages in out_stream to the Stream Manager