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

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

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