public function getDescendants(AbstractNestedNode $node, $depth = null, $includeNode = false)
    {
        $q = $this->createQueryBuilder('n')
                ->andIsDescendantOf($node, !$includeNode);

        if (null !== $depth) {
            $q->andLevelIsLowerThan($node->getLevel() + $depth);
        }

        return $q->orderBy('n._leftnode', 'asc')
                        ->getQuery()
                        ->getResult();
    }