code: async function getOldManifest () {
    try {
      var data = await getFile('.manifest.json.gz')
    } catch (err) {
      if (err.code === 'NoSuchKey') return {}
      else throw err
    }
    var unzippedBody = zlib.gunzipSync(data.Body)
    return JSON.parse(unzippedBody)
  }
docs: Download, unzip, and parse the manifest from remote storage