Both the pickle and copy modules of the standard library make use of a class’s __reduce__() method for customizing the pickle/copy process. They seem to have a consistent view of the first 5 elements of the returned tuple:
(func, args, state, listiter, dictiter) but the 6th element seems different. For pickle it’s state_setter, a callable with signature state_setter(obj, state)->None, but for copy it’s deepcopy with signature deepcopy(arg: T, memo) -> T.
What’s the recommended way to write the callable for the 6th element of the return tuple of __reduce__() so that it can work with both pickle and copy?