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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_version(self, app_id, version):
 """Get the configuration of an app at a specific version. :param str app_id: application ID :param str version: application version :return: application configuration :rtype: :class:`marathon.models.app.MarathonApp` """

        response = self._do_request('GET', '/v2/apps/{app_id}/versions/{version}'
                                    .format(app_id=app_id, version=version))
        return MarathonApp.from_json(response.json())