in cassovary-core/src/main/scala/com/twitter/cassovary/graph/Traverser.scala [177:183]
def +=(kv: (Int, Color)) {
kv._2 match {
case Unenqueued => ()
case Enqueued => if (get(kv._1) == Unenqueued) map.recordInfo(kv._1, false)
case Visited => if (get(kv._1) != Visited) map.recordInfo(kv._1, true)
}
}