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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 clean_super_features(self):
 """ Removes any null & non-integer values from the super feature list """

        if self.super_features:
            self.super_features = [int(sf) for sf in self.super_features
                                   if sf is not None and is_valid_digit(sf)]