code: protected function createAggregationQueryWithContentIdAndLanguageAndVersion($contentId, $language, $version = null)
      {
          $qa = $this->createAggregationQueryWithLanguage($language);
          $qa->match(
              array(
                  'contentId' => $contentId
              )
          );
          if (is_null($version)) {
              $qa->sort(array('createdAt' => -1));
          } else {
              $qa->match(array('version' => $version));
          }
  
          return $qa;
      }
docs: @param string      $contentId
  @param string      $language
  @param string|null $version
  
  @return Stage