docs: def get_assessment_parts(self):
          """Gets the ``AssessmentPartList`` resulting from a search.
  
          return: (osid.assessment.authoring.AssessmentPartList) - the
                  assessment part list
          raise:  IllegalState - list has already been retrieved
          *compliance: mandatory -- This method must be implemented.*
  
          """
          if self.retrieved:
              raise errors.IllegalState('List has already been retrieved.')
          self.retrieved = True
          return objects.AssessmentPartList(self._results, runtime=self._runtime)