unregisterListener method
Unregister listener for Key.
The other registered listeners for key
will be remained.
Implementation
void unregisterListener({
required String key,
required ValueChanged<String?> listener,
}) {
final listenersForKey = _listeners[key];
if (listenersForKey == null || listenersForKey.isEmpty) {
return;
}
listenersForKey.remove(listener);
_listeners[key] = listenersForKey;
}