/guava/guava/src/com/google/common/graph/Traverser.java
order.insertInto(horizon, successors);
if ( successors.hasNext ( ) ) { order.insertInto ( horizon, successors ) ; }
@CheckForNull protected N computeNext() { do { N next = visitNext(horizon); if (next != null) { Iterator<? extends N> successors = successorFunction.successors(next).iterator(); <extra_id_0> return next; } } while (!horizon.isEmpty()); return endOfData(); } };