public function addKeywordsFilter($keywords)
    {
        $contentIds = $this->_em->getRepository('BackBee\NestedNode\KeyWord')
                                ->getContentsIdByKeyWords($keywords);
        if (is_array($contentIds) && !empty($contentIds)) {
            $this->andWhere('cc._uid in(:keywords)')->setParameter('keywords', $contentIds);
        }
    }