}

  @Override
  @CheckForNull
  public V edgeValueOrDefault(N nodeU, N nodeV, @CheckForNull V defaultValue) {
    return delegate().edgeValueOrDefault(nodeU, nodeV, defaultValue);
  }

  @Override
  @CheckForNull
  public V edgeValueOrDefault(EndpointPair<N> endpoints, @CheckForNull V defaultValue) {
    return delegate().edgeValueOrDefault(endpoints, defaultValue);
  }

            .build();

    assertThat(graph.nodes()).containsExactly("A", "B");
    assertThat(graph.edges()).containsExactly(EndpointPair.ordered("A", "B"));
    assertThat(graph.edgeValueOrDefault("A", "B", null)).isEqualTo(10);
  }

  @Test
  public void immutableValueGraphBuilder_putEdgeFromEndpointPair() {
    ImmutableValueGraph<String, Integer> graph =
        ValueGraphBuilder.directed()

      }
    };
  }

  @Override
  public Optional<V> edgeValue(N nodeU, N nodeV) {
    return Optional.ofNullable(edgeValueOrDefault(nodeU, nodeV, null));
  }

  @Override
  public Optional<V> edgeValue(EndpointPair<N> endpoints) {
    return Optional.ofNullable(edgeValueOrDefault(endpoints, null));
  }

  @Override
  public final boolean equals(@CheckForNull Object obj) {
    if (obj == this) {

  }

  @Override
  @CheckForNull
  public V edgeValueOrDefault(N nodeU, N nodeV, @CheckForNull V defaultValue) {
    return edgeValueOrDefaultInternal(checkNotNull(nodeU), checkNotNull(nodeV), defaultValue);
  }

  @Override
  @CheckForNull
  public V edgeValueOrDefault(EndpointPair<N> endpoints, @CheckForNull V defaultValue) {
    validateEndpoints(endpoints);

            .build();

    assertThat(graph.nodes()).containsExactly("A", "B");
    assertThat(graph.edges()).containsExactly(EndpointPair.ordered("A", "B"));
    assertThat(graph.edgeValueOrDefault("A", "B", null)).isEqualTo(10);
  }

  @Test
  public void immutableValueGraphBuilder_putEdgeFromEndpointPair() {
    ImmutableValueGraph<String, Integer> graph =
        ValueGraphBuilder.directed()

    return Maps.asMap(
        graph.edges(),
        edge ->
            // requireNonNull is safe because the endpoint pair comes from the graph.
            requireNonNull(graph.edgeValueOrDefault(edge.nodeU(), edge.nodeV(), null)));
  }

    Function<N, V> successorNodeToValueFn =
        (N successorNode) ->
            // requireNonNull is safe because the endpoint pair comes from the graph.
            requireNonNull(graph.edgeValueOrDefault(node, successorNode, null));
    return graph.isDirected()
        ? DirectedGraphConnections.ofImmutable(
            node, graph.incidentEdges(node), successorNodeToValueFn)

    Function<N, V> successorNodeToValueFn =
        (N successorNode) ->
            // requireNonNull is safe because the endpoint pair comes from the graph.
            requireNonNull(graph.edgeValueOrDefault(node, successorNode, null));
    return graph.isDirected()
        ? DirectedGraphConnections.ofImmutable(
            node, graph.incidentEdges(node), successorNodeToValueFn)