Sylius\Bundle\TaxonomyBundle\Doctrine\ORM\TaxonRepository::findRootNodes PHP Method

    public function findRootNodes()
    {
        $queryBuilder = $this->createQueryBuilder('o');
        $queryBuilder->andWhere($queryBuilder->expr()->isNull($this->getPropertyName('parent')))->orderBy('o.position');
        return $queryBuilder->getQuery()->getResult();
    }