code: def update_assessment_part(self, assessment_part_id, assessment_part_form):
          
          # Implemented from template for
          # osid.resource.ResourceAdminSession.update_resource_template
          collection = JSONClientValidated('assessment_authoring',
                                           collection='AssessmentPart',
                                           runtime=self._runtime)
          if not isinstance(assessment_part_form, ABCAssessmentPartForm):
              raise errors.InvalidArgument('argument type is not an AssessmentPartForm')
          if not assessment_part_form.is_for_update():
              raise errors.InvalidArgument('the AssessmentPartForm is for update only, not create')
          try:
              if self._forms[assessment_part_form.get_id().get_identifier()] == UPDATED:
                  raise errors.IllegalState('assessment_part_form already used in an update transaction')
          except KeyError:
              raise errors.Unsupported('assessment_part_form did not originate from this session')
          if not assessment_part_form.is_valid():
              raise errors.InvalidArgument('one or more of the form elements is invalid')
          collection.save(assessment_part_form._my_map)
  
          self._forms[assessment_part_form.get_id().get_identifier()] = UPDATED
  
          # Note: this is out of spec. The OSIDs don't require an object to be returned:
          return objects.AssessmentPart(
              osid_object_map=assessment_part_form._my_map,
              runtime=self._runtime,
              proxy=self._proxy)
docs: Updates an existing assessment part.
  
          arg:    assessment_part_id (osid.id.Id): the ``Id`` of the
                  ``AssessmentPart``
          arg:    assessment_part_form
                  (osid.assessment.authoring.AssessmentPartForm): part
                  form
          raise:  NotFound - ``assessment_part_id`` not found
          raise:  NullArgument - ``assessment_part_id`` is ``null``
          raise:  OperationFailed - unable to complete request
          raise:  PermissionDenied - authorization failure occurred
          raise:  Unsupported - ``assessment_part_form`` is not of this
                  service
          *compliance: mandatory -- This method must be implemented.*