public function process(Model $model)
    {
        $hiddenOnModel = $model->getHidden();

        foreach ($this->unhidden as $unhidden) {

            if (($key = array_search($unhidden, $hiddenOnModel)) !== false) {

                unset($hiddenOnModel[ $key ]);
            }
        }

        $hiddenOnModel = array_merge($hiddenOnModel, $this->hidden);

        $model->setHidden($hiddenOnModel);

        return $model;
    }