The example on https://docs.python.org/3/library/copyreg.html does not work: 

```
        import copyreg, copy, pickle
        class C:
            def __init__(self, a):
                self.a = a
    
        def pickle_c(c):
            print("pickling a C instance...")
            return C, (c.a,)
    
        copyreg.pickle(C, pickle_c)
        c = C(1)
        d = copy.copy(c)
    
>       p = pickle.dumps(c)
E       AttributeError: Can't pickle local object 'RoadRunnerPickleTests.test_ex.<locals>.C'

picklable_swig_tests.py:133: AttributeError
```