availabilityStream property
Returns stream of availability changes. Listening to this stream is preferred if you need to know whether ad is available as soon as possible.
Implementation
Stream<bool> get availabilityStream => _startWithFuture(
isAvailable, simpleEvents)
.where((event) =>
event == AdEventType.available || event == AdEventType.unavailable)
.map((event) => event == AdEventType.available)
.asBroadcastStream();