code: func (s *promScope) NewScope(scopes ...string) Scope {
  	return &promScope{
  		prefix:         append(s.prefix, scopes...),
  		autoRegisterer: s.autoRegisterer,
  		registerer:     s.registerer,
  	}
  }
docs: // NewScope generates a new Scope prefixed by this Scope's prefix plus the
  // prefixes given joined by periods