public static function getRequiredPermissions()
    {
        $class = get_called_class();
        // If the user is accessing LeftAndMain directly, only generic permissions are required.
        if ($class === self::class) {
            return 'CMS_ACCESS';
        }
        $code = Config::inst()->get($class, 'required_permission_codes');
        if ($code === false) {
            return false;
        }
        if ($code) {
            return $code;
        }
        return 'CMS_ACCESS_' . $class;
    }