docs: def get_grade_system_query_session(self):
          """Gets the ``OsidSession`` associated with the grade system query service.
  
          return: (osid.grading.GradeSystemQuerySession) - a
                  ``GradeSystemQuerySession``
          raise:  OperationFailed - unable to complete request
          raise:  Unimplemented - ``supports_grade_system_query()`` is
                  ``false``
          *compliance: optional -- This method must be implemented if
          ``supports_grade_system_query()`` is ``true``.*
  
          """
          if not self.supports_grade_system_query():
              raise errors.Unimplemented()
          # pylint: disable=no-member
          return sessions.GradeSystemQuerySession(runtime=self._runtime)