public function isRootLabel(\stdClass $label)
    {
        $q = $this->db
            ->select('taxonomy_term_hierarchy', 'h')
            ->condition('h.parent', 0)
            ->condition('h.tid', $label->tid)
            ->fields('h', array('tid'))
            ->range(0, 1)
            ->execute();

        return !empty($q->fetch());
    }