throws InvocationTargetException, IllegalAccessException {
    T returnValue = factory.invoke(null, args.toArray());
    if (returnValue == null) {
      Assert.assertTrue(
          factory + " returns null but it's not annotated with @Nullable", isNullable(factory));
    }
    return returnValue;
  }

  /**

  // To avoid a self retain cycle under j2objc, we store null instead of
  // a reference to 'this'. To access the delegate iterable, call #getDelegate(), which converts
  // null back to 'this'.
  private final @Nullable Iterable<E> iterableDelegate;

  /** Constructor for use by subclasses. */
  protected FluentIterable() {
    this.iterableDelegate = null;
  }

  FluentIterable(Iterable<E> iterable) {

  // To avoid a self retain cycle under j2objc, we store null instead of
  // a reference to 'this'. To access the delegate iterable, call #getDelegate(), which converts
  // null back to 'this'.
  private final @Nullable Iterable<E> iterableDelegate;

  /** Constructor for use by subclasses. */
  protected FluentIterable() {
    this.iterableDelegate = null;
  }

  FluentIterable(Iterable<E> iterable) {

   * excluded from the automated null tests performed by this method.
   */
  @Test
  public void testNulls() throws Exception {
    for (Class<?> classToTest : findClassesToTest(loadClassesInPackage(), NULL_TEST_METHOD_NAMES)) {
      if (classToTest.getSimpleName().equals("ReflectionFreeAssertThrows")) {
        /*
         * These classes handle null properly but throw IllegalArgumentException for the default

    return (connectionsU != null) && connectionsU.successors().contains(nodeV);
  }

  private final @Nullable V edgeValueOrDefaultInternal(N nodeU, N nodeV, @Nullable V defaultValue) {
    GraphConnections<N, V> connectionsU = nodeConnections.get(nodeU);
    V value = (connectionsU == null) ? null : connectionsU.value(nodeV);

   * excluded from the automated null tests performed by this method.
   */
  @Test
  public void testNulls() throws Exception {
    for (Class<?> classToTest : findClassesToTest(loadClassesInPackage(), NULL_TEST_METHOD_NAMES)) {
      if (classToTest.getSimpleName().equals("ReflectionFreeAssertThrows")) {
        /*
         * These classes handle null properly but throw IllegalArgumentException for the default

  final boolean directed;
  boolean allowsSelfLoops = false;
  ElementOrder<N> nodeOrder = ElementOrder.insertion();
  ElementOrder<N> incidentEdgeOrder = ElementOrder.unordered();

  @Nullable Integer expectedNodeCount = null;

  /**
   * Creates a new instance with the specified edge directionality.
   *
   * @param directed if true, creates an instance for graphs whose edges are each directed; if

    if (connections == null) {
      checkNotNull(node);
      throw new IllegalArgumentException(String.format(NODE_NOT_IN_GRAPH, node));
    }
    return connections;
  }

  final N checkedReferenceNode(E edge) {
    N referenceNode = edgeToReferenceNode.get(edge);
    if (referenceNode == null) {
      checkNotNull(edge);

 */
public final class NetworkBuilder<N, E> extends AbstractGraphBuilder<N> {
  boolean allowsParallelEdges = false;
  ElementOrder<? super E> edgeOrder = ElementOrder.insertion();
  @Nullable Integer expectedEdgeCount = null;

  /** Creates a new instance with the specified edge directionality. */
  private NetworkBuilder(boolean directed) {
    super(directed);
  }

  /** Returns a {@link NetworkBuilder} for building directed networks. */

def get_invalid_none():
    return None
```

This way the data will be correctly validated, you won't have an internal server error, and the documentation will also reflect that this *path operation* could return `None` (or `null` in JSON).

### Fixes