public String toSerialForm() {
        var b = new StringBuilder();
        var first = true;
        for (FieldOrder fieldOrder : fieldOrders) {
            if (first) {
                first = false;
            } else {
                b.append(' ');
            }
            fieldOrder.appendSerialForm(b, true);
        }
        return b.toString();
    }
Returns the field orders of this sort specification as list. This is never null but can be empty.
This list can be modified to change this sort spec.
container-search/src/main/java/com/yahoo/search/query/Sorting.java