code: func (v *TreeModel) IterNthChild(iter *TreeIter, parent *TreeIter, n int) bool {
  	c := C.gtk_tree_model_iter_nth_child(v.native(), iter.native(), parent.native(), C.gint(n))
  	return gobool(c)
  }
docs: // IterNthChild is a wrapper around gtk_tree_model_iter_nth_child().