/guava/android/guava/src/com/google/common/graph/Traverser.java
return topDown( InsertionOrder.BACK) ;
return topDown ( startNodes, InsertionOrder.BACK ) ;
horizon.removeFirst(); return null; } }; } final Iterator<N> breadthFirst(Iterator<? extends N> startNodes) { <extra_id_0> } final Iterator<N> preOrder(Iterator<? extends N> startNodes) { return topDown(startNodes, InsertionOrder.FRONT); } private Iterator<N> topDown(Iterator<? extends N> startNodes, InsertionOrder order) { Deque<Iterator<? extends N>> horizon = new ArrayDeque<>();