@classmethod
def subscribe(cls, session, extension='', only_new=False):
    """
        Subscribe to events from the APIC that pertain to instances of this
        class.

        :param session:  the instance of Session used for APIC communication
        :param only_new: Boolean indicating whether to get all events or only the new events. All events (indicated by
                         setting only_new to False) will queue a create event for all of the currently existing objects.
                         Setting only_new to True will only queue events that occur after the initial subscribe. The
                         default has only_new set to False.
        """
    urls = cls._get_subscription_urls()
    for url in urls:
        url += extension
        resp = session.subscribe(url, only_new=only_new)
        if resp is not None:
            if not resp.ok:
                return False
    return True
