code: func (it *LinksTo) Stats() graph.IteratorStats {
  	subitStats := it.primaryIt.Stats()
  	// TODO(barakmich): These should really come from the quadstore itself
  	checkConstant := int64(1)
  	nextConstant := int64(2)
  	st := graph.IteratorStats{
  		NextCost:     nextConstant + subitStats.NextCost,
  		ContainsCost: checkConstant + subitStats.ContainsCost,
  		Next:         it.runstats.Next,
  		Contains:     it.runstats.Contains,
  		ContainsNext: it.runstats.ContainsNext,
  	}
  	st.Size, st.ExactSize = it.Size()
  	return st
  }
docs: // Return a guess as to how big or costly it is to next the iterator.