@abc.abstractmethod<EOL><INDENT>def get_gradebook_ids_by_grade_system(self, grade_system_id):<DEDENT>
return<EOL>
Gets the list of ``Gradebook``  ``Ids`` mapped to a ``GradeSystem``.

        :param grade_system_id: ``Id`` of a ``GradeSystem``
        :type grade_system_id: ``osid.id.Id``
        :return: list of gradebook ``Ids``
        :rtype: ``osid.id.IdList``
        :raise: ``NotFound`` -- ``grade_system_id`` is not found
        :raise: ``NullArgument`` -- ``grade_system_id`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

        *compliance: mandatory -- This method must be implemented.*