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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 subclasses(cls, lst=None):
    '''Recursively gather subclasses of cls.
    '''
    if lst is None:
        lst = []
    for sc in cls.__subclasses__():
        if sc not in lst:
            lst.append(sc)
        subclasses(sc, lst=lst)
    return lst