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

  private Multiset<N> predecessorsMultiset() {
    Multiset<N> predecessors = getReference(predecessorsReference);
    if (predecessors == null) {
      predecessors = HashMultiset.create(inEdgeMap.values());

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

  private Multiset<N> predecessorsMultiset() {
    Multiset<N> predecessors = getReference(predecessorsReference);
    if (predecessors == null) {
      predecessors = HashMultiset.create(inEdgeMap.values());

  if (!attr) return false;
  return !attr.getValue().empty();
}

// Returns the predecessors of `op` when `op`'s predecessors are wrapped by
// islands.
llvm::SmallVector<Operation*> IslandPredecessors(Operation* op) {
  llvm::SmallVector<Operation*> predecessors;
  for (Value operand : op->getOperands()) {
    if (Operation* pred = operand.getDefiningOp()) {

      // expected-remark@above {{Predecessors: {6}}}
      // expected-remark@above {{Successors: {8}}}
      tf_executor.yield %read3 : tensor<32xf32>
      // expected-remark@above {{ID: 8}}
      // expected-remark@above {{Predecessors: {4,5,7}}}
    }
    tf_executor.fetch %island#0 : tensor<32xf32>
    // expected-remark@above {{ID: 10}}
    // expected-remark@above {{Predecessors: {9}}}
  }

        }
        assertThat(
                graph.predecessors(node).contains(adjacentNode)
                    || graph.successors(node).contains(adjacentNode))
            .isTrue();
      }

      for (N predecessor : sanityCheckSet(graph.predecessors(node))) {
        assertThat(graph.successors(predecessor)).contains(node);
        assertThat(graph.hasEdgeConnecting(predecessor, node)).isTrue();

    const auto predecessors =
        side_effect_analysis.DirectControlPredecessors(&sub_op);
    // Get the controls from the predecessors.
    llvm::SmallVector<Value, 4> predecessor_controls;
    predecessor_controls.reserve(predecessors.size());
    for (auto predecessor : predecessors) {
      predecessor_controls.push_back(new_control_for_sub_ops[predecessor]);
    }

  /** Remove {@code node} from the set of predecessors. */
  void removePredecessor(N node);

  /**
   * Remove {@code node} from the set of successors. Returns the value previously associated with
   * the edge connecting the two nodes.
   */
  @CanIgnoreReturnValue
  @CheckForNull
  V removeSuccessor(N node);

  /**
   * Add {@code node} as a predecessor to the origin node. In the case of an undirected graph, it

    assume().that(graphIsMutable()).isTrue();

    addNode(N2);
    Set<Integer> predecessors = graph.predecessors(N2);
    UnsupportedOperationException e =
        assertThrows(UnsupportedOperationException.class, () -> predecessors.add(N1));
    putEdge(N1, N2);
    assertThat(graph.predecessors(N2)).containsExactlyElementsIn(predecessors);
  }

  @Override
  @Test
  public void successors_checkReturnedSetMutability() {

  /** Remove {@code node} from the set of predecessors. */
  void removePredecessor(N node);

  /**
   * Remove {@code node} from the set of successors. Returns the value previously associated with
   * the edge connecting the two nodes.
   */
  @CanIgnoreReturnValue
  @CheckForNull
  V removeSuccessor(N node);

  /**
   * Add {@code node} as a predecessor to the origin node. In the case of an undirected graph, it

 * which has a method {@code getParents()} that retrieves its predecessors in a graph:
 *
 * <pre>{@code
 * someGraphAlgorithm(startNode, MyNode::getParents);
 * }</pre>
 *
 * <p>If you have some other mechanism for returning the predecessors of a node, or one that doesn't
 * return a {@code Iterable<? extends N>}, then you can use a lambda to perform a more general