func NewURLsMap(s string) (URLsMap, error) {
	m := parse(s)

	cl := URLsMap{}
	for name, urls := range m {
		us, err := NewURLs(urls)
		if err != nil {
			return nil, err
		}
		cl[name] = us
	}
	return cl, nil
}
func NewURLsMap(s string) (URLsMap, error) {
	m := parse(s)

	cl := URLsMap{}
	for name, urls := range m {
		us, err := NewURLs(urls)
		if err != nil {
			return nil, err
		}
		cl[name] = us
	}
	return cl, nil
}
// NewURLsMap returns a URLsMap instantiated from the given string,
// which consists of discovery-formatted names-to-URLs, like:
// mach0=http://1.1.1.1:2380,mach0=http://2.2.2.2::2380,mach1=http://3.3.3.3:2380,mach2=http://4.4.4.4:2380