Folder (or namespace) issue on subscriber

[xDaizu]

I've been banging my head to write a simple subscriber for JMS Serializer for 2 days. Finally, after trying many syntaxes unsuccessfully I found vendor/jms/serializer/src/JMS/Serializer/EventDispatcher/Subscriber/DoctrineProxySubscriber.php and just copy pasted it... and still didn't work.

My subscriber reads like this:

<?php

namespace License\StudentBundle\EventListener;

use Doctrine\ORM\PersistentCollection;
use Doctrine\Common\Persistence\Proxy;
use Doctrine\ORM\Proxy\Proxy as ORMProxy;
use JMS\Serializer\EventDispatcher\PreSerializeEvent;
use JMS\Serializer\EventDispatcher\EventSubscriberInterface;


class ProgenitorSerializationSubscriber implements EventSubscriberInterface
{
    public function onPreSerialize(PreSerializeEvent $event)
    {
        throw new \Exception("Preserializiiiiing");
    }

    public static function getSubscribedEvents()
    {
        return array(
            array('event' => 'serializer.pre_serialize', 'method' => 'onPreSerialize'),
        );
    }
}

and it doesn't work. But if I just move it to the vendor/jms/serializer/src/JMS/Serializer/EventDispatcher/Subscriber folder a rename its namespace to namespace License\StudentBundle\EventListener; it works! (or rather doesn't because it throws an exception, haha)

Anyways... WTH? What's going on (or rather isn't going on) behind the scenes? How do I make it work?