public function getContentsParentUids($contentUids)
    {
        $contentUids = (array) $contentUids;
        if (0 === count($contentUids)) {
            return [];
        }

        $contentUids = implode(', ', array_unique(array_map(function ($uid) {
            return '"'.$uid.'"';
        }, $contentUids)));

        $parentUids = $this->_em->getConnection()->executeQuery(
            sprintf('SELECT parent_uid FROM content_has_subcontent WHERE content_uid IN (%s)', $contentUids)
        )->fetchAll(\PDO::FETCH_COLUMN);

        return array_merge($parentUids, $this->getContentsParentUids($parentUids));
    }