def level_order(self) -> Iterator["BSP"]:
        """Iterate over this BSP's hierarchy in level order.

        .. versionadded:: 8.3
        """
        next = [self]  # type: List['BSP']
        while next:
            level = next  # type: List['BSP']
            next = []
            yield from level
            for node in level:
                next.extend(node.children)
Iterate over this BSP's hierarchy in level order.

        .. versionadded:: 8.3