protected function resolveRouteGroupAttributes($namespace = null, array $attributes = [])
    {
        if (is_array($namespace)) {
            $attributes = $namespace;
            $namespace  = '';
        }
        if (!is_null($namespace)) {
            $attributes['namespace'] = empty($namespace) ? $this->namespace : "{$this->namespace}\\{$namespace}";
        }
        return $attributes;
    }