code: func (s *RPC) SendSubmit(destination uint64, request *orderer.SubmitRequest) error {
  	if s.Logger.IsEnabledFor(zapcore.DebugLevel) {
  		defer s.submitSent(time.Now(), destination, request)
  	}
  
  	stream, err := s.getOrCreateStream(destination, SubmitOperation)
  	if err != nil {
  		return err
  	}
  
  	req := &orderer.StepRequest{
  		Payload: &orderer.StepRequest_SubmitRequest{
  			SubmitRequest: request,
  		},
  	}
  
  	s.submitLock.Lock()
  	defer s.submitLock.Unlock()
  
  	err = stream.Send(req)
  	if err != nil {
  		s.unMapStream(destination, SubmitOperation)
  	}
  	return err
  }
docs: // SendSubmit sends a SubmitRequest to the given destination node.