protected function cleanUpContentHardDelete(AbstractClassContent $content)
    {
        $this->_em->getConnection()->executeUpdate(
            'DELETE FROM indexation WHERE owner_uid = :uid',
            [
                'uid' => $content->getUid(),
            ]
        );

        $revisions = $this->_em->getRepository('BackBee\ClassContent\Revision')->findBy(['_content' => $content]);
        foreach ($revisions as $revision) {
            $this->_em->remove($revision);
        }

        return $this;
    }