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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 set_default(self):
 """ Set this key as the default key :returns: An updated list of added keys """

        req = self.request(self.mist_client.uri+'/keys/'+self.id)
        req.post()
        self.is_default = True
        self.mist_client.update_keys()