code: func (it *HasA) NextContains(ctx context.Context) bool {
  	if it.resultIt == nil {
  		return false
  	}
  	for it.resultIt.Next(ctx) {
  		it.runstats.ContainsNext += 1
  		link := it.resultIt.Result()
  		if clog.V(4) {
  			clog.Infof("Quad is %v", it.qs.Quad(link))
  		}
  		if it.primaryIt.Contains(ctx, link) {
  			it.result = it.qs.QuadDirection(link, it.dir)
  			return true
  		}
  	}
  	it.err = it.resultIt.Err()
  	return false
  }
docs: // NextContains() is shared code between Contains() and GetNextResult() -- calls next on the
  // result iterator (a quad iterator based on the last checked value) and returns true if
  // another match is made.