private static function parse(string $headers): array
    {
        $header  = [];
        $matches = [];
        preg_match_all(
                '=^(.[^: ]+): ([^\r\n]*)=m',
                $headers,
                $matches,
                PREG_SET_ORDER
        );
        foreach ($matches as $line) {
            $header[$line[1]] = $line[2];
        }

        return $header;
    }