private function generateSuffix($slug, $list)
    {
        // loop through list and get highest index number
        $index = $list->map(function ($s) use ($slug) {
            // str_replace instead of explode('-');
            return intval(str_replace($slug . '-', '', $s));
        })->sort()->last();

        return $slug . '-' . ($index + 1);
    }