@Override
    public String toString() {
        if (places.size() == 0) {
            return "[]";
        }

        StringBuilder sb = new StringBuilder();
        sb.append(places.size());
        sb.append("\\[");
        sb.append(places.get(0));
        for (int i = 1; i < places.size(); i++) {
            sb.append(", ");
            sb.append(places.get(i));
        }
        sb.append("]");
        return sb.toString();
    }