public function toSnakeCase(): Utility
    {
        $string = mb_ereg_replace('\B([A-Z])', '-\1', trim($this->string));

        $string = mb_strtolower($string, $this->encoding);

        $string = mb_ereg_replace('[-_\s]+', '_', $string);

        return new static($string, $this->encoding);
    }