docs: private String getCacheFormatEntry() throws IOException {
          ZipEntry zipEntry = zipFile.getEntry(CACHE_FORMAT_ENTRY);
          InputStream is = zipFile.getInputStream(zipEntry);
          try {
              Scanner s = new Scanner(is, "UTF-8").useDelimiter("\\A");
              String tag = null;
              if (s.hasNext()) tag = s.next();
              return tag;
          } finally {
              is.close();
          }
      }