public function orderByLevel($reverse = false)
    {
        if ($reverse) {
            return $this
                ->addDescendingOrderByColumn(ChildCategory::LEVEL_COL)
                ->addDescendingOrderByColumn(ChildCategory::LEFT_COL);
        } else {
            return $this
                ->addAscendingOrderByColumn(ChildCategory::LEVEL_COL)
                ->addAscendingOrderByColumn(ChildCategory::LEFT_COL);
        }
    }