An EventSubscriber knows himself what events he is interested in.
If an EventSubscriber is added to an EventManager, the manager invokes
Doctrine\Common\EventSubscriber::getSubscribedEvents() and registers the subscriber as a listener for all
Author: Guilherme Blanco firstname.lastname@example.org
Author: Jonathan Wage email@example.com
Author: Roman Borschel firstname.lastname@example.org
Located at Common/EventSubscriber.php