message: [Keras] fix an example
diff: @@ -245,7 +245,7 @@ def cifar_cnn_model_concat():
  ot2 = cifar_cnn_sub(input_tensor2, 2)
  model2 = Model(input_tensor2, ot2)
  print(model2.summary())
  - output_tensor = Concatenate(axis=1)([model1.output_tensor, model2.output_tensor])
  + output_tensor = Concatenate(axis=1)([model1.output, model2.output])
  output_tensor = MaxPooling2D(pool_size=(2,2), strides=(2,2), padding="valid")(output_tensor)
  output_tensor = Conv2D(filters=64, kernel_size=(3,3), strides=(1,1), padding=(1,1), activation="relu", name="conv2d_0_4")(output_tensor)
  output_tensor = Conv2D(filters=64, kernel_size=(3,3), strides=(1,1), padding=(1,1), activation="relu")(output_tensor)
  