public static function instance_form_validation($mform, $data, $errors) {
        $fspath = clean_param(trim($data['fs_path'], '/'), PARAM_PATH);
        if (empty($fspath) && !is_numeric($fspath)) {
            $errors['fs_path'] = get_string('invalidadminsettingname', 'error', 'fs_path');
        }
        return $errors;
    }