private function addWhere($qb, $where, $prefix = '')
    {
        $prefix = '' !== $prefix ? $prefix . '.' : '';
        $and = $qb->expr()->andX();
        foreach ($where as $k => $v) {
            $and->add($qb->expr()->eq($prefix . $k, "'" . $v . "'"));
        }
        $qb->where($and);

        return $qb;
    }