docs: def get_items(self, assessment_id):
          """Gets the items in sequence from an assessment.
  
          arg:    assessment_id (osid.id.Id): the ``Id`` of the
                  ``Assessment``
          return: (osid.assessment.ItemList) - list of items
          raise:  NotFound - ``assessmentid`` not found
          raise:  NullArgument - ``assessment_id`` is ``null``
          raise:  OperationFailed - unable to complete request
          raise:  PermissionDenied - authorization failure occurred
          *compliance: mandatory -- This method must be implemented.*
  
          """
          if assessment_id.get_identifier_namespace() != 'assessment.Assessment':
              raise errors.InvalidArgument
          return self._part_item_session.get_assessment_part_items(self._get_first_part_id(assessment_id))