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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def annotations_class(cls):
 """Works like annotations, but is only applicable to classes. """

    assert(isclass(cls))
    # To play it safe we avoid to modify the dict while iterating over it,
    # so we previously cache keys.
    # For this we don't use keys() because of Python 3.
    # Todo: Better use inspect.getmembers here
    keys = [key for key in cls.__dict__]
    for key in keys:
        memb = cls.__dict__[key]
        if _check_as_func(memb):
            annotations_func(memb)
        elif isclass(memb):
            annotations_class(memb)
    return cls