public function setSourceLanguage($sourceLanguage): void
    {
        if (!preg_match('#[a-zA-Z]{1,8}(-[a-zA-Z0-9]{1,8})*#', $sourceLanguage)) {
            throw new \InvalidArgumentException('Invalid language string: "' . $sourceLanguage . '"');
        }
        $this->getFileElement()->setAttributeNS(static::XLIFF_NS, 'source-language', $sourceLanguage);
    }