public function replaceNonAlpha(string $replacement = '', bool $strict = false): Utility
    {
        if ($strict) {
            $pattern = '/[^a-zA-Z]/';
        } else {
            $pattern = '/[^a-zA-Z ]/';
        }

        $string = preg_replace($pattern, $replacement, trim($this->string));

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