When there are multiple generics in a class hierarchy, Python can easily

hit a situation where it can't create a consistent MRO during

construction. This is particularly annoying when we're trying to add

generics to older code.
The best solution seems to be to put Generic[...] as the last parent

class instead of the first. In fact, the new PEP-695 syntax for generics

does exactly this.

Ran unit tests.