public function getMorphByUserRelation($relationship)
    {
        return $this->morphedByMany(
            Config::get('laratrust.user_models')[$relationship],
            'user',
            Config::get('laratrust.tables.permission_user'),
            Config::get('laratrust.foreign_keys.permission'),
            Config::get('laratrust.foreign_keys.user')
        );
    }