toXML method
Implementation
@override
String toXML() {
return '''
<?xml version="1.0" encoding="utf-8"?>
<cupps xmlns="$xmlns" messageID="$messageID" xmlns:xsi="$xsi" messageName="$messageName">
<$messageName result="$result">
${dataList.map((e) => e.toXML()).join()}
</$messageName>
</cupps>
''';
}