The stubs for `unittest.TestCase.assertCountEqual()` specify the parameters are Sequences; in fact the method works fine with Iterables, as the first thing the method does is convert them to lists. [1] The docs do say sequences, but it appears there is no reason they cannot be Iterables.
[1]: https://github.com/python/cpython/blob/master/Lib/unittest/case.py#L1156
