def key_slice(self, start_key, end_key, reverse=False):
return (k for k, v in self.iter_items(start_key, end_key, reverse=reverse))<EOL>
T.key_slice(start_key, end_key) -> key iterator:
        start_key <= key < end_key.

        Yields keys in ascending order if reverse is False else in descending order.