@Override
    public String format() {
        if (interval == null) {
            return String.format("%s FOR %s AS %s", getName(), timeAttr.format(), timeAttr.format());
        }
        if (timeUnit == null) {
            return String.format("%s FOR %s AS %s - INTERVAL %s %s", getName(), timeAttr.format(),
                    timeAttr.format(), interval.format(), TimeUnit.SECOND.name());
        }
        return String.format("%s FOR %s AS %s - INTERVAL %s %s", getName(), timeAttr.format(),
                timeAttr.format(), interval.format(), timeUnit.format());
    }
defines the field for generating watermarks
inlong-sort/sort-common/src/main/java/org/apache/inlong/sort/protocol/transformation/WatermarkField.java