/guava/guava/src/com/google/common/graph/DirectedGraphConnections.java
NodeConnection<N> nodeConnection = nodeConnections.next ( ) ; boolean added = seenNodes.add ( nodeConnection.node ) ;
Set<N> seenNodes = new HashSet<>(); return new AbstractIterator<N>() { @Override @CheckForNull protected N computeNext() { while (nodeConnections.hasNext()) { <extra_id_0> if (added) { return nodeConnection.node; } } return endOfData(); }