code: def _handle_unknown_command(self):
          
          while self.query_socket.getsockopt(zmq.RCVMORE):
              # Making sure we 'empty' enveloped message. Otherwise, we can't
              # respond.
              self.query_socket.recv()
          self.query_socket.send(b"ERROR Unknown request type")
docs: Handle an unknown RES command.
  
          The function makes sure to recv all message parts and respond with an
          error.