@utilities.arguments_not_none<EOL><INDENT>def get_grade_system_by_grade(self, grade_id):<DEDENT>
raise errors.Unimplemented()<EOL>
Gets the ``GradeSystem`` by a ``Grade``  ``Id``.

        arg:    grade_id (osid.id.Id): ``Id`` of a ``Grade``
        return: (osid.grading.GradeSystem) - the grade system
        raise:  NotFound - ``grade_id`` not found
        raise:  NullArgument - ``grade_id`` is ``null``
        raise:  OperationFailed - unable to complete request
        raise:  PermissionDenied - authorization failure
        *compliance: mandatory -- This method is must be implemented.*