code: func (w *Writer) SetLevels(levels map[string]string) {
  	w.mutex.Lock()
  	w.setLevels(levels)
  	w.mutex.Unlock()
  }
docs: // SetLevels sets a list of levels and their associated actions.
  // It replaces any existing level/effect mapping. If an unknown
  // effect is supplied, a message is logged.