private final ElementOrder<N> nodeOrder;

  final MapIteratorCache<N, GraphConnections<N, V>> nodeConnections;

  long edgeCount; // must be updated when edges are added or removed

  /** Constructs a graph with the properties specified in {@code builder}. */
  StandardValueGraph(AbstractGraphBuilder<? super N> builder) {
    this(
        builder,
        builder.nodeOrder.<N, GraphConnections<N, V>>createMap(

 */
interface ArchetypeGraph<N> extends SuccessorsFunction<N>, PredecessorsFunction<N> {
  //
  // Graph-level accessors
  //

  /** Returns all nodes in this graph, in the order specified by {@link #nodeOrder()}. */
  Set<N> nodes();

  //
  // Graph properties
  //

  /**
   * Returns true if the edges in this graph are directed. Directed edges connect a {@link

        NetworkBuilder.directed()
            .allowsSelfLoops(true)
            .nodeOrder(ElementOrder.<String>natural())
            .<String, Integer>immutable()
            .build();

    assertThat(emptyNetwork.isDirected()).isTrue();
    assertThat(emptyNetwork.allowsSelfLoops()).isTrue();
    assertThat(emptyNetwork.nodeOrder()).isEqualTo(ElementOrder.<String>natural());
  }

  /**

        ValueGraphBuilder.directed()
            .allowsSelfLoops(true)
            .nodeOrder(ElementOrder.<String>natural())
            .<String, Integer>immutable()
            .build();

    assertThat(emptyGraph.isDirected()).isTrue();
    assertThat(emptyGraph.allowsSelfLoops()).isTrue();
    assertThat(emptyGraph.nodeOrder()).isEqualTo(ElementOrder.<String>natural());
  }

  /**

    assertThat(graph.nodes()).isEqualTo(asNetwork.nodes());
    assertThat(graph.edges()).hasSize(asNetwork.edges().size());
    assertThat(graph.nodeOrder()).isEqualTo(asNetwork.nodeOrder());
    assertThat(graph.isDirected()).isEqualTo(asNetwork.isDirected());
    assertThat(graph.allowsSelfLoops()).isEqualTo(asNetwork.allowsSelfLoops());

    AbstractGraphTest.validateGraph(asGraph);
    assertThat(graph.nodes()).isEqualTo(asGraph.nodes());
    assertThat(graph.edges()).isEqualTo(asGraph.edges());
    assertThat(graph.nodeOrder()).isEqualTo(asGraph.nodeOrder());
    assertThat(graph.incidentEdgeOrder()).isEqualTo(asGraph.incidentEdgeOrder());
    assertThat(graph.isDirected()).isEqualTo(asGraph.isDirected());

    AbstractGraphTest.validateGraph(asGraph);
    assertThat(graph.nodes()).isEqualTo(asGraph.nodes());
    assertThat(graph.edges()).isEqualTo(asGraph.edges());
    assertThat(graph.nodeOrder()).isEqualTo(asGraph.nodeOrder());
    assertThat(graph.incidentEdgeOrder()).isEqualTo(asGraph.incidentEdgeOrder());
    assertThat(graph.isDirected()).isEqualTo(asGraph.isDirected());

      }

      @Override
      public boolean allowsSelfLoops() {
        return AbstractBaseGraph.this.allowsSelfLoops();
      }

      @Override
      public ElementOrder<N> nodeOrder() {
        return AbstractBaseGraph.this.nodeOrder();
      }

      @Override
      public ElementOrder<EndpointPair<N>> edgeOrder() {
        return ElementOrder.unordered(); // Graph doesn't define edge order
      }

    assertThat(graph.nodes()).isEqualTo(asNetwork.nodes());
    assertThat(graph.edges()).hasSize(asNetwork.edges().size());
    assertThat(graph.nodeOrder()).isEqualTo(asNetwork.nodeOrder());
    assertThat(graph.isDirected()).isEqualTo(asNetwork.isDirected());
    assertThat(graph.allowsSelfLoops()).isEqualTo(asNetwork.allowsSelfLoops());