public function toArray()
    {
        $args = func_get_args();
        if ($args) {
            $attributes = [];
            foreach ($args as $key) {
                if ($this->hasAttribute($key)) {
                    $attributes[$key] = $this->get($key);
                }
            }
            return $attributes;
        } else {
            return $this->attributes;
        }
    }