[Question] When is it absolutely necessary to use a `Lambda` layer? about keras HOT 1 OPEN

Lambda layer allows you to apply custom function to the input data, ex: preprocess_input,
One of the example from the sequential model is https://keras.io/examples/generative/ddim/#kernel-inception-distance

Lambda can be used in both Functional and Sequential models.
For more details on Lambda you can refer https://keras.io/api/layers/core_layers/lambda/

You can also use preprocess_input in the custom function like below.

def preprocess(image, label):
      resized_image = tf.image.resize(image, [224, 224])
      final_image = keras.applications.xception.preprocess_input(resized_image)
      return final_image, label

from keras.