def get_gradebook_admin_session(self):
raise Unimplemented()<EOL>
Gets the OsidSession associated with the gradebook administration service.

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