code: public static UTF8String fromBytes(byte[] bytes, int offset, int numBytes) {
      if (bytes != null) {
        return new UTF8String(bytes, BYTE_ARRAY_OFFSET + offset, numBytes);
      } else {
        return null;
      }
    }
docs: Creates an UTF8String from byte array, which should be encoded in UTF-8.
  
  Note: `bytes` will be hold by returned UTF8String.