public function beforeDelete(Event $event, Entity $entity)
    {
        $orderField = $this->_config['order'];
        list($order, $scope) = $this->_getOldValues($entity);

        $this->_sync(
            [$orderField => $this->_getUpdateExpression('-')],
            [$orderField . ' >' => $order],
            $scope
        );
    }