code: func (w *Unbuffered) Clean() error {
  	w.mu.Lock()
  	for _, sw := range w.writers {
  		sw.Close()
  	}
  	w.writers = nil
  	w.mu.Unlock()
  	return nil
  }
docs: // Clean closes and removes all writers. Last non-eol-terminated part of data
  // will be saved.