def get_activity_form_for_update(self, activity_id=None):
if activity_id is None:<EOL><INDENT>raise NullArgument()<EOL><DEDENT>try:<EOL><INDENT>url_path = construct_url('<STR_LIT>',<EOL>bank_id=self._catalog_idstr,<EOL>act_id=activity_id)<EOL>activity = objects.Activity(self._get_request(url_path))<EOL><DEDENT>except Exception:<EOL><INDENT>raise<EOL><DEDENT>activity_form = objects.ActivityForm(activity._my_map)<EOL>self._forms[activity_form.get_id().get_identifier()] = not UPDATED<EOL>return activity_form<EOL>
Gets the activity form for updating an existing activity.
        A new activity form should be requested for each update
        transaction.
        arg:    activityId (osid.id.Id): the Id of the Activity
        return: (osid.learning.ActivityForm) - the activity form
        raise:  NotFound - activityId is not found
        raise:  NullArgument - activityId is null
        raise:  OperationFailed - unable to complete request
        raise:  PermissionDenied - authorization failure
        compliance: mandatory - This method must be implemented.