code: public function renderRichResponseItem()
      {
          $out = [];
          $mediaResponse = [];
  
          $mediaResponse['mediaType'] = 'AUDIO';
  
          $mediaObjects = [];
          foreach ($this->mediaObjects as $mediaObject) {
              $mediaObjects[] = $mediaObject->render();
          }
  
          if (count($mediaObjects) > 0) {
              $mediaResponse['mediaObjects'] = $mediaObjects;
          }
  
          $out['mediaResponse'] = $mediaResponse;
  
          return $out;
      }
docs: Render a single Rich Response item as array.
  
  @return null|array