@Override
    public DependentNodesSet addMustPredecessor(Node fromNode) {
        mustPredecessors.add(fromNode);
        return this;
    }

    @Override
    public void visitAllNodes(Consumer<Node> visitor) {
        dependencyPredecessors.visitAllNodes(visitor);
        for (Node node : mustPredecessors) {
            visitor.accept(node);
        }
        for (Node node : finalizers) {

        public DependentNodesSet addMustPredecessor(Node fromNode) {
            return new DependencyPredecessorsOnlyNodeSet().addMustPredecessor(fromNode);
        }

        @Override
        public void visitAllNodes(Consumer<Node> visitor) {
        }
    };

    /**
     * The dependency predecessors, in order.
     */
    default SortedSet<Node> getDependencyPredecessors() {
        return ImmutableSortedSet.of();

    }

    @Override
    public DependentNodesSet addMustPredecessor(Node fromNode) {
        return new ComplexDependentNodesSet(this).addMustPredecessor(fromNode);
    }

    @Override
    public void visitAllNodes(Consumer<Node> visitor) {
        for (Node node : dependencyPredecessors) {
            visitor.accept(node);
        }
    }

     */
    protected void visitAllNodesWaitingForThisNode(Consumer<Node> visitor) {
        dependentNodes.visitAllNodes(visitor);
    }

    /**
     * Called prior to attempting to schedule a node.
     */
    public void prepareForScheduling() {
        ExecutionState initialState = getInitialState();