How to use the tinify.ServerError function in tinify

tinify.fromBuffer(sourceData).toBuffer((err, resultData) => {
        if (err instanceof tinify.AccountError) {
          reject(err)
          return new Notification('compress filed', {
            body: 'Verify your API key and account limit.'
          })
        } else if (err instanceof tinify.ServerError) {
          reject(err)
          return new Notification('compress filed', {
            body: 'Temporary issue with the Tinify API.'
          })
        } else if (err instanceof tinify.ConnectionError) {
          reject(err)
          return new Notification('compress filed', {
            body: 'A network connection error occurred.'
          })
        } else {
          resolve({compressFile: resultData, distSize: parseInt(resultData.length / 1024)})
        }
      })
    })

tinify.fromBuffer(fileInfo.data).toBuffer(function(err, resultData) {
                if (err instanceof tinify.AccountError && __keys.length > 1) {
                    //更换秘钥
                    __keys.splice(0, 1);
                    tinifyCompress();
                } else if (err instanceof tinify.ServerError && __serverErrorRetry -- > 0) {
                    tinifyCompress();
                } else if(err){
                    reject(err);
                } else {
                    resolve({
                        dir: fileInfo.dir,
                        compressionData: resultData
                    });
                }
            });
        })();