addArrow(pe, e);
addArrow(pe, e, "deletion object dependency");
                public void onDelete(DeleteEvent e) {                    Collection pes =                        m_events.getReachablePropertyEvents(e.getObject());                    for (Iterator it = pes.iterator(); it.hasNext(); ) {                        PropertyEvent pe = (PropertyEvent) it.next();                        addArrow(pe, e);                        Object arg;                        if (pe instanceof SetEvent) {                            if (pe.getArgument() != null) {                                throw new IllegalStateException                                    ("nonnull set arg reachable from delete");                            }                            arg = ((SetEvent) pe).getPreviousValue();                        } else {                            arg = pe.getArgument();                        }                        addLinkDependency                            (pe.getProperty(), m_events.getLastEvent(arg), e);                    }                }