@Override
    public void write(FieldUpdate update) {
        putInt(null, update.getField().getId());
        putInt(null, update.getValueUpdates().size());
        for (ValueUpdate vupd : update.getValueUpdates()) {
            putInt(null, vupd.getValueUpdateClassID().id);
            vupd.serialize(this, update.getField().getDataType());
        }
    }
Write out the value of weighted set field

@param field - field description (name and data type)
@param ws    - field value
document/src/main/java/com/yahoo/document/serialization/VespaDocumentSerializer6.java