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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 observe_model(self, model):
 """Make this model observable within the controller The method also keeps track of all observed models, in order to be able to relieve them later on. :param gtkmvc3.Model model: The model to be observed """

        self.__registered_models.add(model)
        return super(ExtendedController, self).observe_model(model)