@abc.abstractmethod<EOL><INDENT>def set_grade_system(self, grade_system_id):<DEDENT>
pass<EOL>
Sets the grade system.

        :param grade_system_id: the new grade system
        :type grade_system_id: ``osid.id.Id``
        :raise: ``InvalidArgument`` -- ``grade_system_id`` is invalid
        :raise: ``NoAccess`` -- ``grade_system_id`` cannot be modified
        :raise: ``NullArgument`` -- ``grade_system_id`` is ``null``

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