code: def _auto_send(self):
          
          while True:
              if time.time() - self.last_send_time > self.config.async_auto_send_interval_millis or \
                              len(self._tx_queue) >= self.config.async_auto_send_amount:
                  self.publish_queue()
docs: auto send blocking function, when the interval or the message size has been reached, publish
          :return: