public function param($key = NULL, $default = NULL)
    {
        if ( !$key ) {
            return $this->attributes->all();
        }

        $path = '';
        $key  = explode('.', $key);
        foreach ($key as $item) {
            if ( !$path ) {
                $path .= $item;
                continue;
            }
            $path .= '[' . $item . ']';
        }

        return $this->attributes->get($path, $default, TRUE);
    }