this.mutableValueGraph =
          graphBuilder.copy().incidentEdgeOrder(ElementOrder.<N>stable()).build();
    }

    /**
     * Adds {@code node} if it is not already present.
     *
     * <p><b>Nodes must be unique</b>, just as {@code Map} keys must be. They must also be non-null.
     *
     * @return this {@code Builder} object
     */
    @CanIgnoreReturnValue

    }
    return nodeConnections.buildOrThrow();
  }

  @SuppressWarnings("unchecked")
  private static <N> GraphConnections<N, Presence> connectionsOf(Graph<N> graph, N node) {
    Function<N, Presence> edgeValueFn =
        (Function<N, Presence>) Functions.constant(Presence.EDGE_EXISTS);
    return graph.isDirected()
        ? DirectedGraphConnections.ofImmutable(node, graph.incidentEdges(node), edgeValueFn)

  @CollectionSize.Require(absent = ZERO)
  public void testComputeIfAbsent_unsupportedPresentExistingValue() {
    try {
      assertEquals(
          "computeIfAbsent(present, returnsCurrentValue) should return present or throw",
          v0(),
          getMap()
              .computeIfAbsent(
                  k0(),
                  k -> {
                    assertEquals(k0(), k);

      this.mutableValueGraph =
          graphBuilder.copy().incidentEdgeOrder(ElementOrder.<N>stable()).build();
    }

    /**
     * Adds {@code node} if it is not already present.
     *
     * <p><b>Nodes must be unique</b>, just as {@code Map} keys must be. They must also be non-null.
     *
     * @return this {@code Builder} object
     */
    @CanIgnoreReturnValue

            Optional.empty<T>()
        )
    }.reduce { acc, next ->
        acc.zip(next) { left, right ->
            when {
                left.isPresent -> {
                    require(!right.isPresent) {
                        "Expected at most one provider to be present"
                    }
                    left
                }
                else -> right
            }
        }

    }

    protected void assertLocalArtifactNotPresent(Artifact artifact) throws Exception {
        ArtifactRepository localRepo = localRepository();

        String path = localRepo.pathOf(artifact);

        File file = new File(localRepo.getBasedir(), path);

        assertFalse(file.exists(), "Local artifact " + file + " should not be present.");
    }

        return when {
            sinceTags.isEmpty() -> {
                fallback?.let { SinceTagStatus.Present(it) } ?: SinceTagStatus.Missing
            }

            sinceTags.all { it == sinceTags.first() } -> {
                (sinceTags.first() ?: fallback)?.let { SinceTagStatus.Present(it) } ?: SinceTagStatus.Missing
            }

            else -> {
                SinceTagStatus.Inconsistent(sinceTags)

  @MapFeature.Require(absent = SUPPORTS_PUT)
  @CollectionSize.Require(absent = ZERO)
  public void testPutIfAbsent_unsupportedPresentExistingValue() {
    try {
      assertEquals(
          "putIfAbsent(present, existingValue) should return present or throw",
          v0(),
          putIfAbsent(e0()));
    } catch (UnsupportedOperationException tolerated) {
    }
    expectUnchanged();
  }

  @MapFeature.Require(absent = SUPPORTS_PUT)

    E duplicate = arrayAndDuplicate.duplicate;

    int firstIndex = getList().indexOf(duplicate);
    int initialSize = getList().size();
    assertTrue("remove(present) should return true", getList().remove(duplicate));
    assertTrue(
        "After remove(duplicate), a list should still contain the duplicate element",
        getList().contains(duplicate));
    assertFalse(

        return map.containsKey(o);
    }

    @Override
    public boolean add(final String o) {
        return map.put(o, PRESENT) == null;
    }

    @Override
    public boolean remove(final Object o) {
        return map.remove(o) == PRESENT;
    }

    @Override
    public void clear() {
        map.clear();
    }