public static function get_self_conversation_parameters() {
        return new external_function_parameters(
            array(
                'userid' => new external_value(PARAM_INT, 'The id of the user who we are viewing self-conversations for'),
                'messagelimit' => new external_value(PARAM_INT, 'Limit for number of messages', VALUE_DEFAULT, 100),
                'messageoffset' => new external_value(PARAM_INT, 'Offset for messages list', VALUE_DEFAULT, 0),
                'newestmessagesfirst' => new external_value(PARAM_BOOL, 'Order messages by newest first', VALUE_DEFAULT, true)
            )
        );
    }