code: def request(self, msg, use_mid=None):
          
          mid = self._get_mid_and_update_msg(msg, use_mid)
          self.send_request(msg)
          return mid
docs: Send a request message, with automatic message ID assignment.
  
          Parameters
          ----------
          msg : katcp.Message request message
          use_mid : bool or None, default=None
  
          Returns
          -------
          mid : string or None
              The message id, or None if no msg id is used
  
          If use_mid is None and the server supports msg ids, or if use_mid is
          True a message ID will automatically be assigned msg.mid is None.
  
          if msg.mid has a value, and the server supports msg ids, that value
          will be used. If the server does not support msg ids, KatcpVersionError
          will be raised.