public Set<EndpointPair<N>> incidentEdges(N node) {
    checkNotNull(node);
    checkArgument(nodes().contains(node), "Node %s is not an element of this graph.", node);
    IncidentEdgeSet<N> incident =
        new IncidentEdgeSet<N>(this, node, IncidentEdgeSet.EdgeType.BOTH) {
          @Override
          public UnmodifiableIterator<EndpointPair<N>> iterator() {
            if (graph.isDirected()) {