public static function toString(array $assoc, string $separator): string
    {
        $parts = [];
        foreach ($assoc as $name => $value) {
            if (true === $value) {
                $parts[] = $name;
            } else {
                $parts[] = $name.'='.self::quote($value);
            }
        }

        return implode($separator.' ', $parts);
    }