从您的链接

DATA_URL = 'https://storage.googleapis.com/tensorflow/tf-keras-datasets/mnist.npz'

path = tf.keras.utils.get_file('mnist.npz', DATA_URL)
with np.load(path) as data:
  train_examples = data['x_train']
  train_labels = data['y_train']
  test_examples = data['x_test']
  test_labels = data['y_test']

train_dataset = tf.data.Dataset.from_tensor_slices((train_examples, train_labels))

data是npzdict，而traion_examples是实际的数组，它不直接将data传递给tensor_slices。