addSubListener method
Implementation
void addSubListener(Type t, NopListener listener) {
if (_attachNopListeners.containsKey(t)) return;
_attachNopListeners[t] = listener;
}
void addSubListener(Type t, NopListener listener) {
if (_attachNopListeners.containsKey(t)) return;
_attachNopListeners[t] = listener;
}