code: func (it *And) Stats() graph.IteratorStats {
  	stats := getStatsForSlice(it.SubIterators())
  	stats.Next = it.runstats.Next
  	stats.Contains = it.runstats.Contains
  	return stats
  }
docs: // and.Stats() lives here in and-iterator-optimize.go because it may
  // in the future return different statistics based on how it is optimized.
  // For now, however, it's pretty static.