code: def get_grade_system_id(self):
          
          # Implemented from template for osid.learning.Activity.get_objective_id
          if not bool(self._my_map['gradeSystemId']):
              raise errors.IllegalState('grade_system empty')
          return Id(self._my_map['gradeSystemId'])
docs: Gets the ``GradeSystem Id`` in which this grade belongs.
  
          return: (osid.id.Id) - the grade system ``Id``
          *compliance: mandatory -- This method must be implemented.*