code: func NewHasA(qs graph.QuadStore, subIt graph.Iterator, d quad.Direction) *HasA {
  	return &HasA{
  		uid:       NextUID(),
  		qs:        qs,
  		primaryIt: subIt,
  		dir:       d,
  	}
  }
docs: // Construct a new HasA iterator, given the quad subiterator, and the quad
  // direction for which it stands.