public static function get_localized_class_fields($class)
    {
        $fieldNames = null;
        $ancestry = array_reverse(ClassInfo::ancestry($class));
        foreach ($ancestry as $className) {
            if (isset(self::$localizedFields[$className])) {
                if ($fieldNames === null) {
                    $fieldNames = array();
                }
                foreach (self::$localizedFields[$className] as $k => $v) {
                    $fieldNames[] = $k;
                }
            }
        }
        return array_unique($fieldNames);
    }