@abc.abstractmethod<EOL><INDENT>def order_items(self, item_ids, assessment_id):<DEDENT>
pass<EOL>
Sequences existing items in an assessment.

        :param item_ids: the ``Id`` of the ``Items``
        :type item_ids: ``osid.id.Id[]``
        :param assessment_id: the ``Id`` of the ``Assessment``
        :type assessment_id: ``osid.id.Id``
        :raise: ``NotFound`` -- ``assessment_id`` is not found or an ``item_id`` is not on ``assessment_id``
        :raise: ``NullArgument`` -- ``assessment_id`` or ``item_ids`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure occurred

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