Return a function that raises a NotImplementedError with a passed node
    name.

def _node_not_implemented(node_name, cls):
    """Return a function that raises a NotImplementedError with a passed node
    name.
    """

    def f(self, *args, **kwargs):
        raise NotImplementedError("{name!r} nodes are not "
                                  "implemented".format(name=node_name))
    return f