docs: def get_score_system_id(self):
          """Gets the grade system ``Id`` for the score.
  
          return: (osid.id.Id) - the grade system ``Id``
          raise:  IllegalState - ``is_scored()`` is ``false``
          *compliance: mandatory -- This method must be implemented.*
  
          """
          # Implemented from template for osid.resource.Resource.get_avatar_id_template
          if not bool(self._my_map['scoreSystemId']):
              raise errors.IllegalState('this AssessmentOffered has no score_system')
          else:
              return Id(self._my_map['scoreSystemId'])