private void assignPositionFieldFromStringIfNonEmpty(Struct value, String elementText, boolean base64) {
        String str = base64 ? Utf8.toString(Base64.getMimeDecoder().decode(elementText)) : elementText;
        str = str.trim();
        if (str.isEmpty()) {
            return;
        }
        DataType valueType = value.getDataType();
        if (valueType.equals(PositionDataType.INSTANCE)) {
            value.assign(PositionDataType.fromString(str));
        }
    }
Optional test and set condition. Common for document/update/remove elements
This variable is either set in VespaXMLFieldReader#read (reader for document)
or in VespaXMLUpdateReader#read (reader for update).
document/src/main/java/com/yahoo/vespaxmlparser/VespaXMLFieldReader.java