def get_descendant_gradebook_query(self):
raise errors.Unimplemented()<EOL>
Gets the query for a gradebook.

        Multiple retrievals produce a nested ``OR`` term.

        return: (osid.grading.GradebookQuery) - the gradebook query
        raise:  Unimplemented -
                ``supports_descendant_gradebook_query()`` is ``false``
        *compliance: optional -- This method must be implemented if
        ``supports_descendant_gradebook_query()`` is ``true``.*