protected function implode(array $list, string $conjunction = "or")
    {
        $last = array_pop($list) ?: "null";
        if ($list) {
            $glue = count($list) > 1 ? ", " : " ";
            return implode($glue, $list) . ', ' .$conjunction . ' ' . $last;
        }
        return $last;
    }