return delegate().inEdges(node);
  }

  @Override
  public Set<E> outEdges(N node) {
    return delegate().outEdges(node);
  }

  @Override
  public EndpointPair<N> incidentNodes(E edge) {
    return delegate().incidentNodes(edge);
  }

  @Override
  public Set<E> adjacentEdges(E edge) {
    return delegate().adjacentEdges(edge);
  }

  @Override
  public int degree(N node) {

    assertThat(network.nodes()).containsExactly("A", "B");
    assertThat(network.edges()).containsExactly(10);
    assertThat(network.incidentNodes(10)).isEqualTo(EndpointPair.ordered("A", "B"));
  }

  @Test
  public void immutableNetworkBuilder_putEdgeFromEndpointPair() {
    ImmutableNetwork<String, Integer> network =
        NetworkBuilder.directed()

    assertThat(network.nodes()).containsExactly("A", "B");
    assertThat(network.edges()).containsExactly(10);
    assertThat(network.incidentNodes(10)).isEqualTo(EndpointPair.ordered("A", "B"));
  }

  @Test
  public void immutableNetworkBuilder_putEdgeFromEndpointPair() {
    ImmutableNetwork<String, Integer> network =
        NetworkBuilder.directed()

  private final ElementOrder<E> edgeOrder;

  final MapIteratorCache<N, NetworkConnections<N, E>> nodeConnections;

  // We could make this a Map<E, EndpointPair<N>>. It would make incidentNodes(edge) slightly
  // faster, but also make Networks consume 5 to 20+% (increasing with average degree) more memory.
  final MapIteratorCache<E, N> edgeToReferenceNode; // referenceNode == source if directed

  private final ElementOrder<E> edgeOrder;

  final MapIteratorCache<N, NetworkConnections<N, E>> nodeConnections;

  // We could make this a Map<E, EndpointPair<N>>. It would make incidentNodes(edge) slightly
  // faster, but also make Networks consume 5 to 20+% (increasing with average degree) more memory.
  final MapIteratorCache<E, N> edgeToReferenceNode; // referenceNode == source if directed

    checkNotNull(nodeU, "nodeU");
    checkNotNull(nodeV, "nodeV");
    checkNotNull(edge, "edge");

    if (containsEdge(edge)) {
      EndpointPair<N> existingIncidentNodes = incidentNodes(edge);
      EndpointPair<N> newIncidentNodes = EndpointPair.of(this, nodeU, nodeV);
      checkArgument(
          existingIncidentNodes.equals(newIncidentNodes),
          REUSING_EDGE,
          edge,

  }

  @Override
  public Iterator<EndpointPair<N>> incidentEdgeIterator(N thisNode) {
    return Iterators.transform(
        adjacentNodeValues.keySet().iterator(),
        (N incidentNode) -> EndpointPair.unordered(thisNode, incidentNode));
  }

  @Override
  @CheckForNull
  public V value(N node) {
    return adjacentNodeValues.get(node);
  }

  @Override
  public void removePredecessor(N node) {

  }

  @Override
  public Iterator<EndpointPair<N>> incidentEdgeIterator(N thisNode) {
    return Iterators.transform(
        adjacentNodeValues.keySet().iterator(),
        (N incidentNode) -> EndpointPair.unordered(thisNode, incidentNode));
  }

  @Override
  @CheckForNull
  public V value(N node) {
    return adjacentNodeValues.get(node);
  }

  @Override
  public void removePredecessor(N node) {