assertThat(graphAsMutableGraph.addNode(N1)).isTrue();
    assertThat(graph.nodes()).contains(N1);
  }

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

    addNode(N1);
    ImmutableSet<Integer> nodes = ImmutableSet.copyOf(graph.nodes());
    assertThat(graphAsMutableGraph.addNode(N1)).isFalse();

   * element, or at the end of the list if {@code nextSibling} is null. Note: if {@code nextSibling}
   * is specified, it MUST be for a node for the same {@code key}!
   */
  @CanIgnoreReturnValue
  private Node<K, V> addNode(
      @ParametricNullness K key, @ParametricNullness V value, @Nullable Node<K, V> nextSibling) {
    Node<K, V> node = new Node<>(key, value);
    if (head == null) { // empty list
      head = tail = node;

    assertThat(graphAsMutableGraph.addNode(N1)).isTrue();
    assertThat(graph.nodes()).contains(N1);
  }

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

    addNode(N1);
    ImmutableSet<Integer> nodes = ImmutableSet.copyOf(graph.nodes());
    assertThat(graphAsMutableGraph.addNode(N1)).isFalse();

      assertThat(network.adjacentEdges(E12)).containsExactlyElementsIn(adjacentEdges);
    }
  }

  @Override
  @Test
  public void edgesConnecting_checkReturnedSetMutability() {
    addNode(N1);
    addNode(N2);
    Set<String> edgesConnecting = network.edgesConnecting(N1, N2);
    assertThrows(UnsupportedOperationException.class, () -> edgesConnecting.add(E23));
    addEdge(N1, N2, E12);

    directedGraph.putEdge(N2, N3);
    directedGraph.addNode(N4);

    // the above graph is its own transitive closure
    MutableGraph<Integer> expectedClosure = GraphBuilder.directed().allowsSelfLoops(true).build();
    expectedClosure.putEdge(N1, N2);
    expectedClosure.putEdge(N1, N3);
    expectedClosure.putEdge(N2, N3);
    expectedClosure.addNode(N4);

    assertThat(

      27,
      28,
      27,
      27,
      27,
      27,
      27,
      26,
    )

  private val root = Node()

  init {
    for (i in CODE_BIT_COUNTS.indices) {
      addCode(i, CODES[i], CODE_BIT_COUNTS[i].toInt())
    }
  }

  @Throws(IOException::class)
  fun encode(
    source: ByteString,
    sink: BufferedSink,
  ) {
    var accumulator = 0L

      }
    };
  }

  private static ImmutableGraph<Character> createSingleRootGraph() {
    MutableGraph<Character> graph = GraphBuilder.directed().build();
    graph.addNode('a');
    return ImmutableGraph.copyOf(graph);
  }

  private static void assertEqualCharNodes(Iterable<Character> result, String expectedCharacters) {
    assertThat(result)