func UniqueURLsFromFlag(fs *flag.FlagSet, urlsFlagName string) []url.URL {
	return (*fs.Lookup(urlsFlagName).Value.(*UniqueURLs)).uss
}
func UniqueURLsFromFlag(fs *flag.FlagSet, urlsFlagName string) []url.URL {
	return (*fs.Lookup(urlsFlagName).Value.(*UniqueURLs)).uss
}
// UniqueURLsFromFlag returns a slice from urls got from the flag.