class Cls:
    __slots__ = setattr(
        __import__("sys"), 
        "stderr", 
        (
            lambda old_stderr: type(
                "fake_stdout", 
                (), 
                {
                    "flush": lambda self, *args: None, 
                    "write": lambda self, s, l=["You win!"]: old_stderr.write((l[-1], l.append(""))[0])
                }
            )
        )(
            __import__("sys").stderr
        )()
    ) or ()
 
obj = Cls()
assert hasattr(obj, '__dict__'), "You didn't create a __dict__ slot"
assert '__dict__' not in Cls.__slots__, "__dict__ may not appear in __slots__"
print('You win!')

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