docs: private boolean isGZip(byte[] bytes) {
          if(bytes == null || bytes.length == 0) {
              return false;
          }
  
          // refer http://www.gzip.org/zlib/rfc-gzip.html#file-format for magic numbers
          if(bytes[0] == 31 && (bytes[1] == 0x8b || bytes[1] == -117)) {
              return true;
          }
  
          return false;
      }