public NavigableSet<Node> getMustSuccessors() {
            return ImmutableSortedSet.of();
        }

        @Override
        public DependencyNodesSet addMustSuccessor(Node toNode) {
            return new DependencySuccessorsOnlyNodeSet().addMustSuccessor(toNode);
        }

        @Override
        public void onNodeComplete(Node node, Node dependency) {
        }

        @Override

    }

    public Set<Node> getShouldSuccessors() {
        return shouldSuccessors;
    }

    public void addMustSuccessor(Node toNode) {
        deprecateLifecycleHookReferencingNonLocalTask("mustRunAfter", toNode);
        updateDependencyNodes(getDependencyNodes().addMustSuccessor(toNode));
        toNode.addMustPredecessor(this);
    }

    public void addFinalizingSuccessor(Node finalized) {

        return this;
    }

    @Override
    public NavigableSet<Node> getMustSuccessors() {
        return orderedMustSuccessors;
    }

    @Override
    public DependencyNodesSet addMustSuccessor(Node toNode) {
        orderedMustSuccessors.add(toNode);
        return this;
    }

    @Override
    public void onNodeComplete(Node node, Node dependency) {
        delegate.onNodeComplete(node, dependency);

    }

    @Override
    public NavigableSet<Node> getMustSuccessors() {
        return ImmutableSortedSet.of();
    }

    @Override
    public DependencyNodesSet addMustSuccessor(Node toNode) {
        return new ComplexDependencyNodesSet(this).addMustSuccessor(toNode);
    }

    /**
     * Notified when a node that is potentially a member of this set has completed.
     */
    @Override