* while writing to it in another. All it does is help with _reading_ from multiple threads
   * concurrently. For more information, see AbstractNetworkTest.concurrentIteration.
   */
  private transient volatile @Nullable Entry<K, V> cacheEntry;

  MapIteratorCache(Map<K, V> backingMap) {
    this.backingMap = checkNotNull(backingMap);
  }

  @CanIgnoreReturnValue

        .containsExactly(
            EndpointPair.unordered(2, 3),
            EndpointPair.unordered(1, 2),
            EndpointPair.unordered(2, 4))
        .inOrder();
  }

  @Test
  public void concurrentIteration() throws Exception {
    graph = ValueGraphBuilder.directed().build();
    graph.putEdgeValue(1, 2, "A");
    graph.putEdgeValue(3, 4, "B");
    graph.putEdgeValue(5, 6, "C");

    int threadCount = 20;

        .containsExactly(
            EndpointPair.unordered(2, 3),
            EndpointPair.unordered(1, 2),
            EndpointPair.unordered(2, 4))
        .inOrder();
  }

  @Test
  public void concurrentIteration() throws Exception {
    graph = ValueGraphBuilder.directed().build();
    graph.putEdgeValue(1, 2, "A");
    graph.putEdgeValue(3, 4, "B");
    graph.putEdgeValue(5, 6, "C");

    int threadCount = 20;