code: def get_grade_system(self, grade_system_id):
          
          # Implemented from template for
          # osid.resource.ResourceLookupSession.get_resource
          # NOTE: This implementation currently ignores plenary view
          collection = JSONClientValidated('grading',
                                           collection='GradeSystem',
                                           runtime=self._runtime)
          result = collection.find_one(
              dict({'_id': ObjectId(self._get_id(grade_system_id, 'grading').get_identifier())},
                   **self._view_filter()))
          return objects.GradeSystem(osid_object_map=result, runtime=self._runtime, proxy=self._proxy)
docs: Gets the ``GradeSystem`` specified by its ``Id``.
  
          In plenary mode, the exact ``Id`` is found or a ``NotFound``
          results. Otherwise, the returned ``GradeSystem`` may have a
          different ``Id`` than requested, such as the case where a
          duplicate ``Id`` was assigned to a ``GradeSystem`` and retained
          for compatibility.
  
          arg:    grade_system_id (osid.id.Id): ``Id`` of the
                  ``GradeSystem``
          return: (osid.grading.GradeSystem) - the grade system
          raise:  NotFound - ``grade_system_id`` not found
          raise:  NullArgument - ``grade_system_id`` is ``null``
          raise:  OperationFailed - unable to complete request
          raise:  PermissionDenied - authorization failure
          *compliance: mandatory -- This method is must be implemented.*