code: func (h *Handler) serialSend(msg *pb.ChaincodeMessage) error {
  	h.serialLock.Lock()
  	defer h.serialLock.Unlock()
  
  	if err := h.chatStream.Send(msg); err != nil {
  		err = errors.WithMessage(err, fmt.Sprintf("[%s] error sending %s", shorttxid(msg.Txid), msg.Type))
  		chaincodeLogger.Errorf("%+v", err)
  		return err
  	}
  
  	return nil
  }
docs: // serialSend serializes msgs so gRPC will be happy