Looks like the multiprocessing changes from python/typeshed#4282 or python/typeshed#4289 are causing some issues.

Yeah, multiprocessing.Queue is no longer a type in the stubs. At runtime it's not type, but it's documented as a class, which makes things confusing: https://docs.python.org/3/library/multiprocessing.html#multiprocessing.Queue

Also, multiprocessing.queues seems to be undocumented, so for a user to annotate code using queues, they need to either read the stubs or the stdlib implementation, which is unfortunate.

Finally, the return type of multiprocessing.Queue is Queue[Any], so the change loses some typing precision. Since multiprocessing.queues.Queue is not very discoverable (as it's undocumented), for many users this may effectively remove the ability to type check queue items.

The above considerations probably explain why multiprocessing.Queue used to be defined as a class, even thought it's not quite true.

Perhaps more worryingly, the change breaks existing code that uses multiprocessing.Queue as a type. I'll create a typeshed issue about this.

Let's move the discussion to python/typeshed#4313.