// Serialize to GraphDef.
  GraphDef graph_def2;
  ASSERT_TRUE(GetGraphDef(graph, &graph_def2));

  // Compare with first GraphDef + added NodeDef.
  NodeDef* added_node = graph_def.add_node();
  *added_node = node_def;
  EXPECT_EQ(graph_def.DebugString(), graph_def2.DebugString());

  // Look up some nodes by name.
  TF_Operation* neg2 = TF_GraphOperationByName(graph, "neg");

      for (auto id = session->last_num_graph_nodes; id < num_nodes; ++id) {
        Node* const node = graph.FindNodeId(id);
        if (node != nullptr && node->IsOp()) {
          NodeDef* const node_def = graph_def.add_node();
          *node_def = node->def();
        }
      }
      *graph_def.mutable_library() = graph.flib_def().ToProto();
      if (flags::Global().more_stack_traces.value()) {

    graph.addNode(node4);
    graph.addNode(node2);
    graph.addNode(node6);
    graph.addNode(node8);

    assertThat(graph.nodeOrder().comparator()).isEqualTo(Ordering.natural());
    assertThat(graph.nodes()).containsExactly(node2, node4, node6, node8).inOrder();
  }

  private static void addNodes(MutableGraph<Integer> graph) {
    graph.addNode(3);
    graph.addNode(1);

    this.backingValueGraph = new StandardMutableValueGraph<>(builder);
  }

  @Override
  BaseGraph<N> delegate() {
    return backingValueGraph;
  }

  @Override
  public boolean addNode(N node) {
    return backingValueGraph.addNode(node);
  }

  @Override
  public boolean putEdge(N nodeU, N nodeV) {
    return backingValueGraph.putEdgeValue(nodeU, nodeV, Presence.EDGE_EXISTS) == null;
  }

  @Override

 * graphs. Instances of this class should be constructed with {@link ValueGraphBuilder}.
 *
 * <p>Time complexities for mutation methods are all O(1) except for {@code removeNode(N node)},
 * which is in O(d_node) where d_node is the degree of {@code node}.
 *
 * @author James Sexton
 * @author Joshua O'Madadhain
 * @author Omar Darwish
 * @param <N> Node parameter type
 * @param <V> Value parameter type
 */

 * graphs. Instances of this class should be constructed with {@link NetworkBuilder}.
 *
 * <p>Time complexities for mutation methods are all O(1) except for {@code removeNode(N node)},
 * which is in O(d_node) where d_node is the degree of {@code node}.
 *
 * @author James Sexton
 * @author Joshua O'Madadhain
 * @author Omar Darwish
 * @param <N> Node parameter type
 * @param <E> Edge parameter type
 */

     *
     * @return this {@code Builder} object
     */
    @CanIgnoreReturnValue
    public Builder<N> addNode(N node) {
      mutableGraph.addNode(node);
      return this;
    }

    /**
     * Adds an edge connecting {@code nodeU} to {@code nodeV} if one is not already present.
     *

        List<BuildStep> firsts =
                add.values().stream().filter(b -> b.predecessors.isEmpty()).toList();
        firsts.stream()
                .filter(addNode -> !org.containsKey(addNode.name))
                .forEach(addNode -> lasts.forEach(orgNode -> addNode.executeAfter(orgNode)));
        add.forEach((name, node) -> org.merge(name, node, this::merge));
        return org;
    }

      NetworkBuilder.directed().<String, String>immutable().addNode("A").build();
  private static final ImmutableNetwork<String, String> IMMUTABLE_NETWORK_B =
      NetworkBuilder.directed().<String, String>immutable().addNode("B").build();

  public PackageSanityTests() {
    MutableNetwork<String, String> mutableNetworkA = NetworkBuilder.directed().build();
    mutableNetworkA.addNode("a");

    assertThrows(UnsupportedOperationException.class, () -> nodes.add(N2));
    addNode(N1);
    assertThat(graph.nodes()).containsExactlyElementsIn(nodes);
  }

  @Override
  @Test
  public void adjacentNodes_checkReturnedSetMutability() {
    assume().that(graphIsMutable()).isTrue();

    addNode(N1);
    Set<Integer> adjacentNodes = graph.adjacentNodes(N1);