Dispatches an event to all registered listeners.
@api
string $eventName The name of the event to dispatch. The name of: the event is the name of the method that is invoked on listeners.
Event $event The event to pass to the event handlers/listeners.: If not supplied, an empty Event instance is created.
Overrides EventDispatcherInterface::dispatch
public function dispatch($eventName, Event $event = null) {
return $this->dispatcher
->dispatch($eventName, $event);
}