code: func (t *deviceDownloadState) GetBlockCounts(folder string) map[string]int {
  	if t == nil {
  		return nil
  	}
  
  	t.mut.RLock()
  	defer t.mut.RUnlock()
  
  	for name, state := range t.folders {
  		if name == folder {
  			return state.GetBlockCounts()
  		}
  	}
  	return nil
  }
docs: // GetBlockCounts returns a map filename -> number of blocks downloaded for the
  // given folder.