code: func (it *And) Contains(ctx context.Context, val graph.Value) bool {
  	graph.ContainsLogIn(it, val)
  	it.runstats.Contains += 1
  	lastResult := it.result
  	if it.checkList != nil {
  		return it.checkContainsList(ctx, val, lastResult)
  	}
  	mainGood := it.primaryIt.Contains(ctx, val)
  	if mainGood {
  		othersGood := it.subItsContain(ctx, val, lastResult)
  		if othersGood {
  			it.result = val
  			return graph.ContainsLogOut(it, val, true)
  		}
  	}
  	if lastResult != nil {
  		it.primaryIt.Contains(ctx, lastResult)
  	}
  	return graph.ContainsLogOut(it, val, false)
  }
docs: // Check a value against the entire iterator, in order.