func (d *DAG) Ghosts() []string {
	var result []string
	for id := range d.children {
		if _, ok := d.parents[id]; !ok {
			result = append(result, id)
		}
	}
	return result
}
func (d *DAG) Ghosts() []string {
	var result []string
	for id := range d.children {
		if _, ok := d.parents[id]; !ok {
			result = append(result, id)
		}
	}
	return result
}
func ( d * DAG ) Ghosts ( ) [ ] string { var result [ ] string for id := range d . children { if _ , ok := d . parents [ id ] ; ! ok { result = append ( result , id ) } } return result }
// Ghosts returns nodes that were referenced as parents but never created.
Ghosts returns nodes that were referenced as parents but never created .