为什么tf.image.grayscale_to_rgb在tensorflow 1.14.0上不起作用？

Question

我正在尝试将MNIST数据集转换为RGB。我使用以下代码执行此操作，但出现错误，它可与tensorflow1.12.0一起使用，但不适用于tensorflow1.14.0（我的项目基于tensorflow1.14.0）。

Private Sub Class_Initialize()
    Set subjectData = New Scripting.Dictionary
    With subjectData
        .Add "name", ""
        .Add "inn", ""
        .Add "ogrn", ""
        .Add "address", ""
    End With
End Sub

我得到的错误：

mnist = tf.keras.datasets.mnist
(x_train, _), (x_test, _) = mnist.load_data()

X = np.concatenate([x_train, x_test])
X = X.reshape((70000, 28, 28, 1))
assert X.shape == (70000, 28, 28, 1)

X = tf.image.grayscale_to_rgb(X, name=None)
assert X.shape == (70000, 28, 28, 3)