code: func (cp *MockChannelProvider) ChannelService(ctx fab.ClientContext, channelID string) (fab.ChannelService, error) {
  
  	if cp.customChannelService != nil {
  		return cp.customChannelService, nil
  	}
  
  	cs := MockChannelService{
  		provider:   cp,
  		channelID:  channelID,
  		transactor: &MockTransactor{},
  		discovery:  NewMockDiscoveryService(nil),
  		selection:  NewMockSelectionService(nil),
  	}
  	return &cs, nil
  }
docs: // ChannelService returns a mock ChannelService