code: func RCSBackends() []string {
  	bes := make([]string, 0, len(rcsNameToBackendMap))
  	for k := range rcsNameToBackendMap {
  		bes = append(bes, k)
  	}
  	sort.Strings(bes)
  	return bes
  }
docs: // RCSBackends returns the list of registered RCS backends.