(self)
Return a post-order iterator for the tree.

        This must be implemented by the concrete subclass.
Return a post-order iterator for the tree.
Return a post - order iterator for the tree .
def post_order(self):
        """
        Return a post-order iterator for the tree.

        This must be implemented by the concrete subclass.
        """
        raise NotImplementedError
def post_order ( self ) : raise NotImplementedError