code: func doRequestSubscription(r *Registry, p *network.Peer, bin uint8, subs map[enode.ID]map[Stream]struct{}) bool {
  	log.Debug("Requesting subscription by registry:", "registry", r.addr, "peer", p.ID(), "bin", bin)
  	// bin is always less then 256 and it is safe to convert it to type uint8
  	stream := NewStream("SYNC", FormatSyncBinKey(bin), true)
  	if streams, ok := subs[p.ID()]; ok {
  		// delete live and history streams from the map, so that it won't be removed with a Quit request
  		delete(streams, stream)
  		delete(streams, getHistoryStream(stream))
  	}
  	err := r.RequestSubscription(p.ID(), stream, NewRange(0, 0), High)
  	if err != nil {
  		log.Debug("Request subscription", "err", err, "peer", p.ID(), "stream", stream)
  		return false
  	}
  	return true
  }
docs: // doRequestSubscription sends the actual RequestSubscription to the peer