code: def send_command(self, cmd, priority=False):
          
          if priority:
              self._pending.insert(0, cmd)
          else:
              self._pending.append(cmd)
          self._pending_size += len(cmd)
  
          if self._pending_size > DEFAULT_PENDING_SIZE:
              yield self._flush_pending()
docs: Flushes a command to the server as a bytes payload.