@abc.abstractmethod<EOL><INDENT>def get_rubric_id(self):<DEDENT>
return<EOL>
Gets the ``Id`` of the rubric.

        :return: an assessment ``Id``
        :rtype: ``osid.id.Id``
        :raise: ``IllegalState`` -- ``has_rubric()`` is ``false``

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