code: protected XmlFile getConfigXml() {
          return new XmlFile(Jenkins.XSTREAM,
                  new File(Jenkins.getInstance().getRootDir(),wrapper.getShortName()+".xml"));
      }
docs: Controls the file where {@link #load()} and {@link #save()}
  persists data.
  
  This method can be also overridden if the plugin wants to
  use a custom {@link XStream} instance to persist data.
  
  @since 1.245