9.1.0
The bulk of the changes are related to how the library entities are now interconnected. In previous versions of aio_pika.Channel instances not contains a link to the aio_pika.Connection instances for now is contains it.
While I don't want custom code to work directly with the aiormq.Channel instance, this was a public API and I should warn you about the change here. The aio_pika.Channel.channel property is deprecated. Use aio_pika.Channel.get_underlay_chanel() instead.
Now all library entities already use this method.