code: func (el *ChannelEventListener) RegSentTransfers() *ChannelEventListener {
  	el.SentTransfer = make(chan bundle.Bundle)
  	el.ids = append(el.ids, el.em.RegisterListener(func(data interface{}) {
  		el.SentTransfer <- data.(bundle.Bundle)
  	}, event.EventSentTransfer))
  	return el
  }
docs: // RegSentTransfers registers this listener to listen for sent off transfers.