respond<T> method
Subscribe EventBus on a specific type of event, and register responder to it.
When T is not given or given as dynamic, it listens to all events regardless of the type.
Returns Subscription, which can be disposed to cancel all the subscription registered to itself.
Implementation
@override
Subscription respond<T>(Responder<T> responder) =>
Subscription(_lastEventSubject).respond<T>(responder);