def get_grading_calculation_manager(self):
raise Unimplemented()<EOL>
Gets the ``GradingCalculationManager``.

        return: (osid.grading.calculation.GradingCalculationManager) - a
                ``GradingCalculationManager``
        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.*