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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 username(self, default=None):
        '''
        Return the full, given, or family name if set.
        '''
        if self.lis_person_name_given:
            return self.lis_person_name_given
        elif self.lis_person_name_family:
            return self.lis_person_name_family
        elif self.lis_person_name_full:
            return self.lis_person_name_full
        else:
            return default