docs: def get_assessments_taken(self):
          """Gets the assessment taken list resulting from the search.
  
          return: (osid.assessment.AssessmentTakenList) - the assessment
                  taken list
          raise:  IllegalState - the assessment taken 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.AssessmentTakenList(self._results, runtime=self._runtime)