bool hasListeners(string $eventName = null) Checks whether an event has any registered listeners
addSubscriber(
removeSubscriber(
mixed getArgument(string $key) Get argument by key.
array getListeners(string $eventName = null) Gets the listeners of a specific event or all listeners
bool hasArgument(string $key) Has argument.
int|null getListenerPriority(string $eventName, callable $listener) Gets the listener priority
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