def update_objective(self, objective_form=None):
if objective_form is None:<EOL><INDENT>raise NullArgument()<EOL><DEDENT>if not isinstance(objective_form, abc_learning_objects.ObjectiveForm):<EOL><INDENT>raise InvalidArgument('<STR_LIT>')<EOL><DEDENT>if not objective_form.is_for_update():<EOL><INDENT>raise InvalidArgument('<STR_LIT>')<EOL><DEDENT>try:<EOL><INDENT>if self._forms[objective_form.get_id().get_identifier()] == UPDATED:<EOL><INDENT>raise IllegalState('<STR_LIT>')<EOL><DEDENT><DEDENT>except KeyError:<EOL><INDENT>raise Unsupported('<STR_LIT>')<EOL><DEDENT>if not objective_form.is_valid():<EOL><INDENT>raise InvalidArgument('<STR_LIT>')<EOL><DEDENT>url_path = construct_url('<STR_LIT>',<EOL>bank_id=self._catalog_idstr)<EOL>try:<EOL><INDENT>result = self._put_request(url_path, objective_form._my_map)<EOL><DEDENT>except Exception:<EOL><INDENT>raise  <EOL><DEDENT>self._forms[objective_form.get_id().get_identifier()] = UPDATED<EOL>return objects.Objective(result)<EOL>
Updates an existing objective.

        arg:    objectiveForm (osid.learning.ObjectiveForm): the form
                containing the elements to be updated
        raise:  IllegalState - objectiveForm already used in an update
                transaction
        raise:  InvalidArgument - the form contains an invalid value
        raise:  NullArgument - objectiveForm is null
        raise:  OperationFailed - unable to complete request
        raise:  PermissionDenied - authorization failure
        raise:  Unsupported - objectiveForm did not originate from
                get_objective_form_for_update()
        compliance: mandatory - This method must be implemented.