code: func (f *Fetcher) Notify(peer string, hash common.Hash, number uint64, time time.Time,
  	headerFetcher headerRequesterFn, bodyFetcher bodyRequesterFn) error {
  	block := &announce{
  		hash:        hash,
  		number:      number,
  		time:        time,
  		origin:      peer,
  		fetchHeader: headerFetcher,
  		fetchBodies: bodyFetcher,
  	}
  	select {
  	case f.notify <- block:
  		return nil
  	case <-f.quit:
  		return errTerminated
  	}
  }
docs: // Notify announces the fetcher of the potential availability of a new block in
  // the network.