/** {@inheritDoc} */
  @Override
  public Object onReceive(@Nullable Object obj) {
    if (obj instanceof byte[]) {
      X.println(">>> Byte array received over REST: " + Arrays.toString((byte[]) obj));

      BigInteger val = new BigInteger((byte[]) obj);

      X.println(">>> Unpacked a BigInteger from byte array received over REST: " + val);

      return val;
    } else return obj;
  }
  /** {@inheritDoc} */
  @Override
  public Object onSend(Object obj) {
    if (obj instanceof BigInteger) {
      X.println(">>> Creating byte array from BigInteger to send over REST: " + obj);

      byte[] bytes = ((BigInteger) obj).toByteArray();

      X.println(
          ">>> Created byte array from BigInteger to send over REST: " + Arrays.toString(bytes));

      return bytes;
    } else return obj;
  }