How to use the pykka.ActorRegistry.get_by_class function in pykka

def test_actors_may_be_looked_up_by_class(
    actor_a_class, a_actor_refs, b_actor_refs
):
    result = ActorRegistry.get_by_class(actor_a_class)

    for a_actor in a_actor_refs:
        assert a_actor in result
    for b_actor in b_actor_refs:
        assert b_actor not in result

def test_broadcast_sends_message_to_all_actors_of_given_class_name(
    actor_a_class, actor_b_class
):
    ActorRegistry.broadcast({'command': 'foo'}, target_class='ActorA')

    for actor_ref in ActorRegistry.get_by_class(actor_a_class):
        received_messages = actor_ref.proxy().received_messages.get()
        assert {'command': 'foo'} in received_messages

    for actor_ref in ActorRegistry.get_by_class(actor_b_class):
        received_messages = actor_ref.proxy().received_messages.get()
        assert {'command': 'foo'} not in received_messages

def test_broadcast_sends_message_to_all_actors_of_given_class_name(
    actor_a_class, actor_b_class
):
    ActorRegistry.broadcast({'command': 'foo'}, target_class='ActorA')

    for actor_ref in ActorRegistry.get_by_class(actor_a_class):
        received_messages = actor_ref.proxy().received_messages.get()
        assert {'command': 'foo'} in received_messages

    for actor_ref in ActorRegistry.get_by_class(actor_b_class):
        received_messages = actor_ref.proxy().received_messages.get()
        assert {'command': 'foo'} not in received_messages

def send(cls, event, **kwargs):
    listeners = pykka.ActorRegistry.get_by_class(cls)
    logger.debug('Sending %s to %s: %s', event, cls.__name__, kwargs)
    for listener in listeners:
        # Save time by calling methods on Pykka actor without creating a
        # throwaway actor proxy.
        #
        # Because we use `.tell()` there is no return channel for any errors,
        # so Pykka logs them immediately. The alternative would be to use
        # `.ask()` and `.get()` the returned futures to block for the listeners
        # to react and return their exceptions to us. Since emitting events in
        # practise is making calls upwards in the stack, blocking here would
        # quickly deadlock.
        listener.tell({
            'command': 'pykka_call',
            'attr_path': ('on_event',),
            'args': (event,),
            'kwargs': kwargs,

def number_of_connections(self):
        return len(pykka.ActorRegistry.get_by_class(self.protocol))

def stop_actors_by_class(klass):
    actors = pykka.ActorRegistry.get_by_class(klass)
    logger.debug('Stopping %d instance(s) of %s', len(actors), klass.__name__)
    for actor in actors:
        actor.stop()