public function getParentContents(AbstractClassContent $content)
    {
        $result = $this->_em->getConnection()
            ->createQueryBuilder()
            ->select('p.parent_uid', 'c.classname')
            ->from('content_has_subcontent', 'p')
            ->leftJoin('p', 'content', 'c', 'p.parent_uid = c.uid')
            ->where('p.content_uid = :uid')
            ->setParameter('uid', $content->getUid())
            ->execute()
            ->fetchAll()
        ;

        $parents = [];
        foreach ($result as $parentData) {
            $parentData['classname'] = AbstractClassContent::getFullClassname($parentData['classname']);
            $parents[] = $this->_em->find($parentData['classname'], $parentData['parent_uid']);
        }

        return $parents;
    }