assertThat(edgeString).contains(edge.toString());

      EndpointPair<N> endpointPair = network.incidentNodes(edge);
      N nodeU = endpointPair.nodeU();
      N nodeV = endpointPair.nodeV();
      assertThat(asGraph.edges()).contains(EndpointPair.of(network, nodeU, nodeV));
      assertThat(network.edgesConnecting(nodeU, nodeV)).contains(edge);

  public Graph<N> asGraph() {
    return new AbstractGraph<N>() {
      @Override
      public Set<N> nodes() {
        return AbstractValueGraph.this.nodes();
      }

      @Override
      public Set<EndpointPair<N>> edges() {
        return AbstractValueGraph.this.edges();
      }

      @Override
      public boolean isDirected() {
        return AbstractValueGraph.this.isDirected();
      }

      @Override

   *     #allowsSelfLoops()}
   * @throws IllegalArgumentException if the endpoints are unordered and the graph is directed
   * @since 27.1
   */
  @CanIgnoreReturnValue
  boolean putEdge(EndpointPair<N> endpoints);

  /**
   * Removes {@code node} if it is present; all edges incident to {@code node} will also be removed.
   *
   * @return {@code true} if the graph was modified as a result of this call
   */

   *     #allowsSelfLoops()}
   * @throws IllegalArgumentException if the endpoints are unordered and the graph is directed
   * @since 27.1
   */
  @CanIgnoreReturnValue
  @Nullable V putEdgeValue(EndpointPair<N> endpoints, V value);

  /**
   * Removes {@code node} if it is present; all edges incident to {@code node} will also be removed.
   *
   * @return {@code true} if the graph was modified as a result of this call

  Set<N> successors();

  /**
   * Returns an iterator over the incident edges.
   *
   * @param thisNode The node that this all of the connections in this class are connected to.
   */
  Iterator<EndpointPair<N>> incidentEdgeIterator(N thisNode);

  /**
   * Returns the value associated with the edge connecting the origin node to {@code node}, or null
   * if there is no such edge.
   */
  @Nullable V value(N node);

          + "that allows self-loops, call allowsSelfLoops(true) on the Builder.";
  static final String NOT_AVAILABLE_ON_UNDIRECTED =
      "Cannot call source()/target() on a EndpointPair from an undirected graph. Consider calling "
          + "adjacentNode(node) if you already have a node, or nodeU()/nodeV() if you don't.";
  static final String EDGE_ALREADY_EXISTS = "Edge %s already exists in the graph.";

      return network.inEdges(node);
    }

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

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

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

     *     #allowsSelfLoops()}
     * @throws IllegalArgumentException if the endpoints are unordered and the graph is directed
     */
    @CanIgnoreReturnValue
    public ImmutableValueGraph.Builder<N, V> putEdgeValue(EndpointPair<N> endpoints, V value) {
      mutableValueGraph.putEdgeValue(endpoints, value);
      return this;
    }

    /**
     * Returns a newly-created {@code ImmutableValueGraph} based on the contents of this {@code