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;
}