def get_grading_calculation_proxy_manager(self):
raise errors.Unimplemented()<EOL>
Gets the ``GradingCalculationProxyManager``.

        return:
                (osid.grading.calculation.GradingCalculationProxyManager
                ) - a ``GradingCalculationProxyManager``
        raise:  OperationFailed - unable to complete request
        raise:  Unimplemented - ``supports_grading_calculation() is
                false``
        *compliance: optional -- This method must be implemented if
        ``supports_grading_calculation()`` is true.*