public static function unRegister($extensions)
    {
        foreach ((array) $extensions as $extension) {
            foreach (static::$_registry as &$registered) {
                $key = array_search($extension, $registered['extensions'], true);
                if (false !== $key) {
                    unset($registered['extensions'][$key]);
                }

                if (empty($registered['extensions'])) {
                    unset($registered);
                }
            }
        }
    }