public function offsetSet($lang, $value)
    {
        if (DataType::isLanguageOrRange($lang)) {
            if (is_null($value)) {
                unset($this->members[$lang]);
            } else {
                $this->members[$lang] = static::checkMember($value);
            }
        } else {
            throw new InvalidArgumentException(
                'JSKOS\LanguageMap may only use language tags or ranges as index'
            );
        }
    }