How to make sure preprocess function is doing what it's supposed to?

[mazatov]

For example, I'm trying out resnet152 and the preprocess_function doesn't seem to do anything. Just giving back the same output.

ResNet18, preprocess_input = Classifiers.get('resnet18')
preprocess_input(np.array([[1000,1],[-2,5]]))
Out[27]: 
array([[1000,    1],
       [  -2,    5]])

[ZFTurbo]

As I remember these models were trained without any preprocessing.

Thier first layer is BatchNorm:

    # resnet bottom
    x = layers.BatchNormalization(name='bn_data', **no_scale_bn_params)(img_input)

[mazatov]

Interesting. I was just basing it on this line:
ResNet18, preprocess_input = Classifiers.get('resnet18')

[ZFTurbo]

Yes. You do it right. preprocess_input for these models returns input as is.