iterator pattern while current left is not nonecurrent current left self stack append(currentreturn self def __next__(self)if len(self stack< raise stopiteration while len(self stack current self stack pop(data current data if current right is not nonecurrent current right self stack append(currentwhile current left is not nonecurrent current left self stack append(currentreturn data raise stopiteration if __name__ ="__main__"tree mytree(node( )tree add_node(node( )tree add_node(node( )tree add_node(node( )tree add_node(node( )tree add_node(node( )tree add_node(node( )tree add_node(node( )tree add_node(node( )for in treeprint(