code: public function getRelatedVideos($videoId)
      {
          $listResponse = $this->search->listSearch('snippet', array('relatedToVideoId' => $videoId, 'type' => 'video'));
          if (empty($listResponse)) {
              throw new \RuntimeException(sprintf('Could not find video with id %s', $videoId));
          }
  
          return $listResponse;
      }
docs: Get related videos
  See https://developers.google.com/youtube/v3/docs/search/list#response for returned value
  
  @param  string $videoId
  @return array