/guava/guava/src/com/google/common/graph/Traverser.java
return checkNotNull ( top.next ( ) ) ;
return new Traversal<N>(tree) { @CheckForNull @Override N visitNext(Deque<Iterator<? extends N>> horizon) { Iterator<? extends N> top = horizon.getFirst(); if (top.hasNext()) { <extra_id_0> } horizon.removeFirst(); return null; } }; }