to.parents.remove(from);
    }

    List<String> visitAll() {
        return visitAll(vertices.values(), new HashMap<>(), new ArrayList<>());
    }

    List<String> findCycle(Vertex vertex) {
        return visitCycle(Collections.singleton(vertex), new HashMap<>(), new LinkedList<>());
    }

    private static List<String> visitAll(

    public List<String> computePhases(Lifecycle lifecycle) {
        Graph graph = new Graph();
        lifecycle.phases().forEach(phase -> addPhase(graph, null, null, phase));
        List<String> allPhases = graph.visitAll();
        Collections.reverse(allPhases);
        List<String> computed =
                allPhases.stream().filter(s -> !s.startsWith("$")).collect(Collectors.toList());