protected function getModuloCharRange($start, $end, $modulo)
    {
        $start = $this->converter->toUnicodeCodepoint($start);
        $end = $this->converter->toUnicodeCodepoint($end);
        $modulo = hexdec($modulo);

        $chars = '';
        for ($start; $start <= $end; $start += $modulo) {
            $chars .= $this->converter->toUTF8Character($start);
        }

        return $chars;
    }