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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 preferred(self):
 """ Get the preferred subtag. :return: preferred :class:`language_tags.Subtag.Subtag` if exists, otherwise None. """

        if 'Preferred-Value' in self.data['record']:
            preferred = self.data['record']['Preferred-Value']
            type = self.data['type']
            if type == 'extlang':
                type = 'language'
            return Subtag(preferred, type)
        return None