Yes,the kata seems to be expecting the 2 types to be the same and no exception should be raised which I found a bit odd.

I didn't solve this kata, but:

>>>from collections import Counter
>>>type(Counter([]))
<class 'collections.Counter'>

In my understanding of the kata, it is not the same type (though it can be subclass).

Unless I misunderstood your post: do you mean the kata expects no exception in such cases? If so, I agreee the description is lacking some specifications.

I believe there are some tests that are wrong: a dict type is not supposed to rais an exception on collections.counter for instance. Any suggestion/clue of why that is?