code: func (t *ProgressEmitter) BytesCompleted(folder string) (bytes int64) {
  	t.mut.Lock()
  	defer t.mut.Unlock()
  
  	for _, s := range t.registry[folder] {
  		bytes += s.Progress().BytesDone
  	}
  	l.Debugf("progress emitter: bytes completed for %s: %d", folder, bytes)
  	return
  }
docs: // BytesCompleted returns the number of bytes completed in the given folder.