for (int64_t i = 0; i < input.NumElements(); ++i) {
    tensorflow::Example example;
    auto* feature_map = example.mutable_features()->mutable_feature();
    (*feature_map)["x"].mutable_float_list()->add_value(i);
    input.flat<tstring>()(i) = example.SerializeAsString();
  }

  const tensorflow::string input_op_name(
      tensorflow::ParseTensorName(input_name).first);
  TF_Operation* input_op =

        callback.onFailure(e);
        return;
      }
      callback.onSuccess(value);
    }

    @Override
    public String toString() {
      return MoreObjects.toStringHelper(this).addValue(callback).toString();
    }
  }

  /**
   * Returns the result of the input {@code Future}, which must have already completed.
   *

    }
  }

  @Override
  public String toString() {
    // TODO(dpb): Better toString, in the style of Futures.transform etc.
    return toStringHelper(this).add("state", state.get()).addValue(future).toString();
  }

  @SuppressWarnings("removal") // b/260137033
  @Override
  protected void finalize() {
    if (state.get().equals(OPEN)) {