code: def delete_objective(self, objective_id=None):
          
          if objective_id is None:
              raise NullArgument()
          if not isinstance(objective_id, abc_id):
              raise InvalidArgument('argument type is not an osid Id')
  
          url_path = construct_url('objectives',
                                   bank_id=self._catalog_idstr,
                                   obj_id=objective_id)
          result = self._delete_request(url_path)
          return objects.Objective(result)
docs: Deletes the Objective identified by the given Id.
  
          arg:    objectiveId (osid.id.Id): the Id of the Objective to
                  delete
          raise:  NotFound - an Objective was not found identified by the
                  given Id
          raise:  NullArgument - objectiveId is null
          raise:  OperationFailed - unable to complete request
          raise:  PermissionDenied - authorization failure
          compliance: mandatory - This method must be implemented.