code: func (l *logger) Facilities() (enabled, disabled []string) {
  	l.mut.Lock()
  	for facility, isEnabled := range l.debug {
  		if isEnabled {
  			enabled = append(enabled, facility)
  		} else {
  			disabled = append(disabled, facility)
  		}
  	}
  	l.mut.Unlock()
  	return
  }
docs: // Facilities returns the currently known set of facilities, both those for
  // which debug is enabled and those for which it is disabled.