code: function isXML(res) {
    return (res.headers['content-type'] &&
            (/^[a-zA-Z]+\/xml/.test(res.headers['content-type']) ||
             /^[a-zA-Z]+\/[a-zA-Z]+\+xml/.test(res.headers['content-type'])));
  
  }
docs: /*
  Given a response object determine if it's some kind of XML