code: func (al *Apps) GetImages() []string {
  	var il []string
  	for _, a := range al.apps {
  		il = append(il, a.Image)
  	}
  	return il
  }
docs: // these convenience functions just return typed lists containing just the named member
  // TODO(vc): these probably go away when we just pass Apps to stage0
  // GetImages returns a list of the images in al, one per app.
  // The order reflects the app order in al.