    def get_subscriber_queue(self, event_types=None):
        """Create a new queue for a specific combination of event types
        and return it.

        Returns:
            a :class:`multiprocessing.Queue`.
        Raises:
            RuntimeError if called after `run`
        """

        try:
            self.started_queue.get(timeout=1)
            raise RuntimeError('Cannot create a new subscriber queue while Exchange is running.')
        except Empty:
            pass

        if event_types is None:
            event_types = EventTypes.ALL

        queue = Queue()
        self.queues[event_types].append(queue)
        return queue
Create a new queue for a specific combination of event types
and return it.

Returns:
a :class:`multiprocessing.Queue`.
Raises:
RuntimeError if called after `run`
bigchaindb/events.py