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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 all_subclasses(cls):
 """Recursively returns all the subclasses of the provided class. """

    subclasses = cls.__subclasses__()
    descendants = (descendant for subclass in subclasses
                   for descendant in all_subclasses(subclass))
    return set(subclasses) | set(descendants)