I'm talking about initialization.

Without this class, if I call `$container->get('cmf_routing_auto.factory')`, all builder services will be initialized and added to a `registerAlias` method call, no matter how many of them are actually used.

With this class, if I call `$container->get('cmf_routing_auto.factory')` only this class and the builder class will be initialized. Only if one of them are used, they are requested from the container and initialized.