code: func (v *ListStore) InsertBefore(sibling *TreeIter) *TreeIter {
  	var ti C.GtkTreeIter
  	C.gtk_list_store_insert_before(v.native(), &ti, sibling.native())
  	iter := &TreeIter{ti}
  	return iter
  }
docs: // InsertBefore() is a wrapper around gtk_list_store_insert_before().