code: def send_pending_requests(self):
          
          try:
              with self._lock:
                  if not self._can_send_recv():
                      return Errors.NodeNotReadyError(str(self))
                  # In the future we might manage an internal write buffer
                  # and send bytes asynchronously. For now, just block
                  # sending each request payload
                  data = self._protocol.send_bytes()
                  total_bytes = self._send_bytes_blocking(data)
              if self._sensors:
                  self._sensors.bytes_sent.record(total_bytes)
              return total_bytes
          except ConnectionError as e:
              log.exception("Error sending request data to %s", self)
              error = Errors.KafkaConnectionError("%s: %s" % (self, e))
              self.close(error=error)
              return error
docs: Can block on network if request is larger than send_buffer_bytes