docs: function onFinish(output) {
      var book = output.getBook();
      var options = output.getOptions();
      var prefix = options.get('prefix');
  
      if (!book.isMultilingual()) {
          return Promise(output);
      }
  
      var filePath = 'index.html';
      var engine = createTemplateEngine(output, filePath);
      var context = JSONUtils.encodeOutput(output);
  
      // Render the theme
      return Templating.renderFile(engine, prefix + '/languages.html', context)
  
      // Write it to the disk
      .then(function(tplOut) {
          return writeFile(output, filePath, tplOut.getContent());
      });
  }