Still able to access raw tensor data after close() is called

まず、提供された再現手順に関係するエントリポイント Tensor.close() と Tensor.asRawTensor().data() を、ConcreteFunction.close() のライフサイクルを含めて追跡します。output.close() 後に raw data にアクセスすると想定どおり IllegalStateException が発生することを確認し、関連するテストが見つかった場合は、この動作のカバレッジを追加または更新します。

System information

• Have I written custom code: see simple test case below to reproduce
• OS Platform and Distribution: Windows 10, 64-bit operating system, x64-based processor
• TensorFlow installed from (source or binary): binary via Maven
• TensorFlow version: v0.4.1
• Java version (i.e., the output of java -version): AdoptOpenJDK-11.0.11+9
• Java command line flags (e.g., GC parameters): N/A
• CUDA/cuDNN version: N/A - using pure CPU version
• GPU model and memory: N/A - using pure CPU version

Describe the current behavior
After closing a tensor output from a concrete function (and the concrete function itself), am still able to access the tensor's raw data.

Describe the expected behavior
Expect an IllegalStateException when accessing the raw tensor data because close() was already called on the tensor.

Code to reproduce the issue

// Create simple (a + b) function
ConcreteFunction addTwoInts = ConcreteFunction.create((tf) -> {
    Placeholder<TInt32> inputA = tf.placeholder(TInt32.class);
    Placeholder<TInt32> inputB = tf.placeholder(TInt32.class);
    Add<TInt32> output = tf.math.add(inputA, inputB);
    return Signature.builder().key("add")
            .input("a", inputA)
            .input("b", inputB)
            .output("out", output)
            .build();
});

// Apply to input
Map<String, Tensor> input = Map.of(
        "a", TInt32.scalarOf(1),
        "b", TInt32.scalarOf(2));
Tensor output = addTwoInts.call(input).get("out");

// Close everything
addTwoInts.close();
output.close();

// Expect java.lang.IllegalStateException: close() was called on the Tensor
output.asRawTensor().data();  // However, no exception is thrown here

Have recently upgraded from v0.2.0, where the same test case setup would throw the excepted exception.