code: public function findOneTransverseBlockByCode($code, $language, $siteId)
      {
          $qa = $this->createAggregationQuery();
          $qa->match(array(
              'code' => $code,
              'language' => $language,
              'siteId' => $siteId,
              'transverse' => true
          ));
  
          return $this->singleHydrateAggregateQuery($qa);
  
      }
docs: @param string $code
  @param string $language
  @param string $siteId
  
  @return ReadBlockInterface|null