code: protected function createAggregationQueryBuilderWithSiteIdAndLanguage($siteId, $language, $transverse)
      {
          $qa = $this->createAggregationQuery();
          $qa->match(array(
              'siteId' => $siteId,
              'language' => $language,
              'transverse' => $transverse
          ));
  
          return $qa;
      }
docs: @param string  $siteId
  @param string  $language
  @param boolean $transverse
  
  @return Stage