def get_grade_system(self):
<EOL>if not bool(self._my_map['<STR_LIT>']):<EOL><INDENT>raise errors.IllegalState('<STR_LIT>')<EOL><DEDENT>mgr = self._get_provider_manager('<STR_LIT>')<EOL>if not mgr.supports_grade_system_lookup():<EOL><INDENT>raise errors.OperationFailed('<STR_LIT>')<EOL><DEDENT>lookup_session = mgr.get_grade_system_lookup_session(proxy=getattr(self, "<STR_LIT>", None))<EOL>lookup_session.use_federated_gradebook_view()<EOL>return lookup_session.get_grade_system(self.get_grade_system_id())<EOL>
Gets the ``GradeSystem`` in which this grade belongs.

        return: (osid.grading.GradeSystem) - the package grade system
        raise:  OperationFailed - unable to complete request
        *compliance: mandatory -- This method must be implemented.*