Fix a bug about wrong order of function arguments

[LostBenjamin]

Hi,

This pull request is a fix to a potential bug about wrong order of function arguments at Lib/test/test_descr.py. Please check the changes.

Best,
Jingxuan

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[serhiy-storchaka]

No, it is the correct order.

[LostBenjamin]

Why?

The documentation says that the first argument of isinstance is the object and the second argument is the class.

[serhiy-storchaka]

The first argument is the object (its value does not matter, it is ignored in this test in any case). The second argument can be not only a class, but also a tuple or an arbitrary object with the __instancecheck__() method. The test checks that isinstance(x, y) calls y.__instancecheck__().

[LostBenjamin]

Thank you for the explanation!