public function userResponsible()
    {
        if (empty($this->user_id)) { return false; }
        if (class_exists($class = '\Cartalyst\Sentry\Facades\Laravel\Sentry')
            || class_exists($class = '\Cartalyst\Sentinel\Laravel\Facades\Sentinel')
        ) {
            return $class::findUserById($this->user_id);
        } else {
            $user_model = app('config')->get('auth.model');

            if (empty($user_model)) {
                $user_model = app('config')->get('auth.providers.users.model');
                if (empty($user_model)) {
                    return false;
                }
            }
            if (!class_exists($user_model)) {
                return false;
            }
            return $user_model::find($this->user_id);
        }
    }