src/EventsTrait.php
protected function getSubscriberClassName($subscriberClass): string
    {
        if ($this->isEventSubscriber($subscriberClass)) {
            return \is_object($subscriberClass) ? \get_class($subscriberClass) : $subscriberClass;
        }

        throw new \InvalidArgumentException('subscriberClass must be an EventSubscriber');
    }
protected function getSubscriberClassName($subscriberClass): string
    {
        if ($this->isEventSubscriber($subscriberClass)) {
            return \is_object($subscriberClass) ? \get_class($subscriberClass) : $subscriberClass;
        }

        throw new \InvalidArgumentException('subscriberClass must be an EventSubscriber');
    }
Get subscriber class name.

@param string|EventSubscriber $subscriberClass

@throws \InvalidArgumentException

@return string