private void addArrow(Event from, Event to) {
private void addArrow(Event from, Event to, String cause) {
    private void addArrow(Event from, Event to) {        LinkedList outgoing = (LinkedList) m_outgoing.get(from);        if (outgoing == null) {            outgoing = new LinkedList();            m_outgoing.put(from, outgoing);        }        setCount(to, getCount(to) + 1);        outgoing.add(to);    }