code: func (cs *MockChannelService) Transactor(reqCtx reqContext.Context) (fab.Transactor, error) {
  	if cs.transactor != nil {
  		return cs.transactor, nil
  	}
  	return &MockTransactor{ChannelID: cs.channelID, Ctx: reqCtx}, nil
  }
docs: // Transactor returns a mock transactor