code: public function getStream($mediaId)
      {
          $response = $this->getHttp()->get(self::API_GET, ['media_id' => $mediaId]);
  
          $response->getBody()->rewind();
  
          $body = $response->getBody()->getContents();
  
          $json = json_decode($body, true);
  
          if (JSON_ERROR_NONE === json_last_error()) {
              $this->checkAndThrow($json);
          }
  
          return $body;
      }
docs: Fetch item from WeChat server.
  
  @param string $mediaId
  
  @return mixed
  
  @throws \EasyWeChat\Core\Exceptions\RuntimeException