code: func (f *Fetcher) forgetBlock(hash common.Hash) {
  	if insert := f.queued[hash]; insert != nil {
  		f.queues[insert.origin]--
  		if f.queues[insert.origin] == 0 {
  			delete(f.queues, insert.origin)
  		}
  		delete(f.queued, hash)
  	}
  }
docs: // forgetBlock removes all traces of a queued block from the fetcher's internal
  // state.