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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 rename_model(self, old_model, new_model):
 """ Change the label of a model attached to the Bundle :parameter str old_model: the current name of the model (must exist) :parameter str new_model: the desired new name of the model (must not exist) :return: None :raises ValueError: if the new_model is forbidden """

        # TODO: raise error if old_feature not found?

        self._check_label(new_model)
        self._rename_label('model', old_model, new_model)