* equivalent to {@code nodes().contains(nodeU) && successors(nodeU).contains(nodeV)}, and to
   * {@code edgeConnectingOrNull(nodeU, nodeV) != null}.
   *
   * <p>In an undirected network, this is equal to {@code hasEdgeConnecting(nodeV, nodeU)}.
   *
   * @since 23.0
   */
  boolean hasEdgeConnecting(N nodeU, N nodeV);

  /**

        CollectResult collectResult = system.collectDependencies(session, collectRequest);

        List<DependencyNode> nodes = collectResult.getRoot().getChildren();
        assertEquals(2, nodes.size());
        checkUtSimpleArtifactDependencies(
                nodes.get(0).getDependency(), nodes.get(1).getDependency());
    }

    @Test
    void testResolveArtifact() throws Exception {

    assertThat(graph.nodes()).containsExactly("A");
    assertThat(graph.edges()).isEmpty();
  }

  @Test
  public void immutableGraphBuilder_putEdgeFromNodes() {
    ImmutableGraph<String> graph =
        GraphBuilder.directed().<String>immutable().putEdge("A", "B").build();

    assertThat(graph.nodes()).containsExactly("A", "B");

    assertThat(graph.nodes()).containsExactly("A");
    assertThat(graph.edges()).isEmpty();
  }

  @Test
  public void immutableGraphBuilder_putEdgeFromNodes() {
    ImmutableGraph<String> graph =
        GraphBuilder.directed().<String>immutable().putEdge("A", "B").build();

    assertThat(graph.nodes()).containsExactly("A", "B");

      "Cannot add self-loop edge on node %s, as self-loops are not allowed. To construct a graph "
          + "that allows self-loops, call allowsSelfLoops(true) on the Builder.";
  static final String NOT_AVAILABLE_ON_UNDIRECTED =
      "Cannot call source()/target() on a EndpointPair from an undirected graph. Consider calling "
          + "adjacentNode(node) if you already have a node, or nodeU()/nodeV() if you don't.";

    * This ensures that attachment and detachment of volumes is independent of any single nodes’ availability. Meaning, if a node or kubelet becomes unavailable for any reason, the volumes attached to that node will be detached so they are free to be attached to other nodes.

        assertThat(network.edgesConnecting(node, adjacentNode))
            .containsExactlyElementsIn(network.edgesConnecting(adjacentNode, node));
      }
    }
  }

  @Override
  @Test
  public void nodes_checkReturnedSetMutability() {
    Set<Integer> nodes = network.nodes();
    assertThrows(UnsupportedOperationException.class, () -> nodes.add(N2));
    addNode(N1);

        // nodes must have a single output.
        if (node->num_outputs() != 1) {
          return InvalidArgument(
              "When `num_opers` is set to -1, nodes referenced in `inputs` "
              "must have a single output. Node ",
              node->name(), " has ", node->num_outputs(),
              " outputs. Encountered while creating function '", fn_name, "'");
        }
      }
    }

  @Test
  public void immutableValueGraphBuilder_addNode() {
    ImmutableValueGraph<String, Integer> graph =
        ValueGraphBuilder.directed().<String, Integer>immutable().addNode("A").build();

    assertThat(graph.nodes()).containsExactly("A");
    assertThat(graph.edges()).isEmpty();
  }

  @Test
  public void immutableValueGraphBuilder_putEdgeFromNodes() {
    ImmutableValueGraph<String, Integer> graph =

        // We already know that nodeU equals other.nodeU. Combined with the earlier statement,
        // and the transitive property of equality, this implies that nodeU equals nodeV.
        // If nodeU equals nodeV, condition1 == condition2, so checking condition1 is sufficient.
        return nodeV().equals(other.nodeV());
      }