}

  @Override
  public Set<N> predecessors() {
    return Collections.unmodifiableSet(((BiMap<E, N>) inEdgeMap).values());
  }

  @Override
  public Set<N> successors() {
    return Collections.unmodifiableSet(((BiMap<E, N>) outEdgeMap).values());
  }

  @Override
  public Set<E> edgesConnecting(N node) {

  }

  @LazyInit private transient @Nullable Reference<Multiset<N>> predecessorsReference;

  @Override
  public Set<N> predecessors() {
    return Collections.unmodifiableSet(predecessorsMultiset().elementSet());
  }

  private Multiset<N> predecessorsMultiset() {
    Multiset<N> predecessors = getReference(predecessorsReference);
    if (predecessors == null) {

            Collection<String> packages,
            String key,
            XmlNode configuration) {
        this.realm = realm;
        this.artifacts = Collections.unmodifiableSet(new HashSet<>(artifacts));
        this.packages = Collections.unmodifiableSet(new HashSet<>(packages));
        this.key = key;
        this.configuration = configuration;
    }

    /**
     * Returns ClassLoader used to load extension classes.

  private final transient Set<E> delegate;

  ForwardingImmutableSet(Set<E> delegate) {
    // TODO(cpovirk): are we over-wrapping?
    this.delegate = Collections.unmodifiableSet(delegate);
  }

  @Override
  public UnmodifiableIterator<E> iterator() {
    return Iterators.unmodifiableIterator(delegate.iterator());
  }

  @Override

    return new UndirectedGraphConnections<>(ImmutableMap.copyOf(adjacentNodeValues));
  }

  @Override
  public Set<N> adjacentNodes() {
    return Collections.unmodifiableSet(adjacentNodeValues.keySet());
  }

  @Override
  public Set<N> predecessors() {
    return adjacentNodes();
  }

  @Override
  public Set<N> successors() {
    return adjacentNodes();
  }

    }

    public CoreExports(ClassRealm realm, Set<String> exportedArtifacts, Set<String> exportedPackages) {
        this.artifacts = Collections.unmodifiableSet(new HashSet<>(exportedArtifacts));
        this.packages = exportedPackages.stream()
                .collect(collectingAndThen(toMap(identity(), v -> realm), Collections::unmodifiableMap));
    }

    /**

  }

  @LazyInit private transient @Nullable Reference<Multiset<N>> adjacentNodesReference;

  @Override
  public Set<N> adjacentNodes() {
    return Collections.unmodifiableSet(adjacentNodesMultiset().elementSet());
  }

  private Multiset<N> adjacentNodesMultiset() {
    Multiset<N> adjacentNodes = getReference(adjacentNodesReference);
    if (adjacentNodes == null) {

    }

    @OutputDirectory
    public DirectoryProperty getOutputDir() {
        return outputDir;
    }

    @Input
    public Set<String> getResources() {
        return Collections.unmodifiableSet(resources);
    }

    @Classpath
    public String getResourcesClasspath() {
        // This will make sure the task is not considered up to date if the resources are changed.

    return adjacentNodes();
  }

  @Override
  public Set<N> successors() {
    return adjacentNodes();
  }

  @Override
  public Set<E> incidentEdges() {
    return Collections.unmodifiableSet(incidentEdgeMap.keySet());
  }

  @Override
  public Set<E> inEdges() {
    return incidentEdges();
  }

  @Override
  public Set<E> outEdges() {
    return incidentEdges();
  }

        this.extension = requireNonNull(extension, "extension");
        this.classifier = classifier;
        this.includesDependencies = includesDependencies;
        this.pathTypes = Collections.unmodifiableSet(new HashSet<>(Arrays.asList(pathTypes)));

        Map<String, String> properties = new HashMap<>();
        properties.put(ArtifactProperties.TYPE, id);
        properties.put(ArtifactProperties.LANGUAGE, language.id());