toXML method
Implementation
String toXML() {
return '''<supportedStock stockName="$stockName" supportsColor="$supportsColor" stockWidth="$stockWidth" stockHeight="$stockHeight" leftMargin="$leftMargin" rightMargin="$rightMargin" topMargin="$topMargin" bottomMargin="$bottomMargin" perforationLeft="$perforationLeft"/>''';
}