code: func (l *logger) FacilityDebugging() []string {
  	enabled := make([]string, 0, len(l.debug))
  	l.mut.Lock()
  	for facility := range l.debug {
  		enabled = append(enabled, facility)
  	}
  	l.mut.Unlock()
  	return enabled
  }
docs: // FacilityDebugging returns the set of facilities that have debugging
  // enabled.