docs: private String generateXml(String encrypt, String signature, String timestamp, String nonce) {
      String format =
          "<xml>\n"
              + "<Encrypt><![CDATA[%1$s]]></Encrypt>\n"
              + "<MsgSignature><![CDATA[%2$s]]></MsgSignature>\n"
              + "<TimeStamp>%3$s</TimeStamp>\n"
              + "<Nonce><![CDATA[%4$s]]></Nonce>\n"
              + "</xml>";
      return String.format(format, encrypt, signature, timestamp, nonce);
    }