@abc.abstractmethod<EOL><INDENT>def get_score(self):<DEDENT>
return<EOL>
Gets the score in this entry if the grading system is not based on grades.

        :return: the score
        :rtype: ``decimal``
        :raise: ``IllegalState`` -- ``is_graded()`` is ``false`` or ``GradeSystem.isBasedOnGrades()`` is ``true``

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