docs: def update_assessment_taken(self, assessment_taken_form):
          """Updates an existing assessment taken.
  
          arg:    assessment_taken_form
                  (osid.assessment.AssessmentTakenForm): the form
                  containing the elements to be updated
          raise:  IllegalState - ``assessment_taken_form`` already used in
                  an update transaction
          raise:  InvalidArgument - the form contains an invalid value
          raise:  NullArgument - ``assessment_taken_form`` is ``null``
          raise:  OperationFailed - unable to complete request
          raise:  PermissionDenied - authorization failure occurred
          raise:  Unsupported - ``assessment_offered_form`` did not
                  originate from
                  ``get_assessment_taken_form_for_update()``
          *compliance: mandatory -- This method must be implemented.*
  
          """
          # Implemented from template for
          # osid.resource.ResourceAdminSession.update_resource_template
          collection = JSONClientValidated('assessment',
                                           collection='AssessmentTaken',
                                           runtime=self._runtime)
          if not isinstance(assessment_taken_form, ABCAssessmentTakenForm):
              raise errors.InvalidArgument('argument type is not an AssessmentTakenForm')
          if not assessment_taken_form.is_for_update():
              raise errors.InvalidArgument('the AssessmentTakenForm is for update only, not create')
          try:
              if self._forms[assessment_taken_form.get_id().get_identifier()] == UPDATED:
                  raise errors.IllegalState('assessment_taken_form already used in an update transaction')
          except KeyError:
              raise errors.Unsupported('assessment_taken_form did not originate from this session')
          if not assessment_taken_form.is_valid():
              raise errors.InvalidArgument('one or more of the form elements is invalid')
          collection.save(assessment_taken_form._my_map)
  
          self._forms[assessment_taken_form.get_id().get_identifier()] = UPDATED
  
          # Note: this is out of spec. The OSIDs don't require an object to be returned:
          return objects.AssessmentTaken(
              osid_object_map=assessment_taken_form._my_map,
              runtime=self._runtime,
              proxy=self._proxy)