def METHOD_NAME(self) -> FrozenMapping[str, Expression]:
    inner_volatile = self._inner.METHOD_NAME()
    if self._index_name in inner_volatile:
        # TODO: use delete method of frozendict
        index_name = self._index_name
        return FrozenDict((name, value) for name, value in inner_volatile.items() if name != index_name)
    else:
        return inner_volatile