def METHOD_NAME(self, volume: str, event_id: str):
    """
    Adds a volume to an event. These are the volumes that will appear on the
    event page. It should include volumes naturally associated with the event
    (by virtue of belonging to the event's venue) as well as colocated volumes.
    :param volume: The full volume ID (e.g., P19-1, 2022.acl-long)
    :param event: The event (e.g., acl-2019, acl-2022)
    """
    self._create_event(event_id)
    if volume not in self.events[event_id]["volumes"]:
        self.events[event_id]["volumes"].append(volume)