code: private void createOEXDirectory(String wuid) throws IOException {
      File oexDirectory = new File(directory, wuid);
      if (!oexDirectory.exists() && !oexDirectory.mkdirs()) {
        throw new WebDriverException("Unable to create directory path: " + directory.getPath());
      }
      File prefsDatPath = new File(oexDirectory, "prefs.dat");
      String prefContent = String.format(WIDGET_PREFS_DAT_CONTENT, wuid);
      Files.write(prefContent, prefsDatPath, Charsets.UTF_8);
    }
docs: Create the minimal directory structure and prefs.dat for an Opera extension.
  
  @param wuid ID of extension as known in widgets.dat