public static function instance(array $values = [])
    {
        if (!self::$instance) {
            self::$instance = static::load($values);
        } elseif ($values) {
            $instance = self::$instance;
            foreach ($values as $key => $value) {
                $instance->offsetSet($key, $value);
            }
        }

        return self::$instance;
    }