def build_get_details_request(token)
        xml = Builder::XmlMarkup.new :indent => 2
        xml.tag! 'GetExpressCheckoutDetailsReq', 'xmlns' => PAYPAL_NAMESPACE do
          xml.tag! 'GetExpressCheckoutDetailsRequest', 'xmlns:n2' => EBAY_NAMESPACE do
            xml.tag! 'n2:Version', API_VERSION