func (self *EventStream) RemoveListener(name string, m *machine.Machine) {
key := fmt.Sprintf("%s-%s", name, m.String())
if _, ok := self.listeners[key]; ok {
delete(self.listeners, key)
}
}
func (self *EventStream) AddListener(name string, m *machine.Machine, l interface{}) {
listener := EventListener{m, l}
key := fmt.Sprintf("%s-%s", name, m.String())
self.listeners[key] = listener
}