groovy get xml attribute value

Could any one help with such xml?

<ResultSet fetchSize="10">
      <Row rowNumber="1">
         <ID>1</ID>
       </Row>
      <Row rowNumber="2">
         <ID>2</ID>
       </Row>

I'm trying to get the value of fetchSize attribute by using groovy

I tried like

ResultSet.value()
ResultSet.text()
ResultSet.size()

but it didn't work is that case

first, I used new XmlParser().parseText(responseAsXml)