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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 get(self, field):
 """ Returns the value of a user field. :param str field: The name of the user field. :returns: str -- the value """

        if field in ('username', 'uuid', 'app_data'):
            return self.data[field]
        else:
            return self.data.get('app_data', {})[field]