@Override
    public void write(FieldPathUpdate update) {
        putByte(null, (byte)update.getUpdateType().getCode());
        put(null, update.getOriginalFieldPath());
        put(null, update.getOriginalWhereClause());
    }
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