public function getForFacet($sorting)
    {
        $noSortingSet = $sorting !== 0 && $sorting !== FALSE && empty($sorting);
        $sortingIsCount = $sorting === 'count' || $sorting === 1 || $sorting === '1' || $sorting === TRUE;
        if ($noSortingSet) {
            return '';
        } elseif ($sortingIsCount) {
            return 'count';
        } else {
            return 'index';
        }
    }