code: private static HashCode sign(Operation value) {
      Hasher h = Hashing.md5().newHasher();
      h.putString(value.getConsumerId(), StandardCharsets.UTF_8);
      h.putChar('\0');
      h.putString(value.getOperationName(), StandardCharsets.UTF_8);
      h.putChar('\0');
      return Signing.putLabels(h, value.getLabels()).hash();
    }
docs: Obtains the {@hashCode} for the contents of {@code value}.
  
  @param value a {@code Operation} to be signed
  @return the {@code HashCode} corresponding to {@code value}