public function contains(Certificate $cert): bool
    {
        $id = self::_getCertKeyId($cert);
        $map = $this->_getKeyIdMap();
        if (!isset($map[$id])) {
            return false;
        }
        foreach ($map[$id] as $c) {
            /** @var Certificate $c */
            if ($cert->equals($c)) {
                return true;
            }
        }
        return false;
    }