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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_model(self, appname, modelname):
 """ return model or None """

        app = self._get_app(appname)
        models = app.get_models()
        model = None
        for mod in models:
            if mod.__name__ == modelname:
                model = mod
                return model
        msg = "Model " + modelname + " not found"