code: func (f *lightFetcher) unregisterPeer(p *peer) {
  	p.lock.Lock()
  	p.hasBlock = nil
  	p.lock.Unlock()
  
  	f.lock.Lock()
  	defer f.lock.Unlock()
  
  	// check for potential timed out block delay statistics
  	f.checkUpdateStats(p, nil)
  	delete(f.peers, p)
  }
docs: // unregisterPeer removes a new peer from the fetcher's peer set