def get_grading_batch_proxy_manager(self):
raise errors.Unimplemented()<EOL>
Gets the ``GradingBatchProxyManager``.

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