}

    @Override
    public Stream<File> unprovenHierarchies() {
        return watchProbesByHierarchy.values().stream()
            .filter(WatchProbe::leftArmed)
            .map(WatchProbe::getWatchableHierarchy);
    }

    @Override
    public void armWatchProbe(File watchableHierarchy) {
        WatchProbe probe = watchProbesByHierarchy.get(watchableHierarchy);
        if (probe != null) {
            try {