Error while runing image_test.py

Hi!
I was having a look at the test functions of the datasets module to try to create my own task & dataset, and I get an error while running image_test.py
ValueError: Dataset imagenet2012_16 with split train doesn't appear to be preprocessed? Please run dataset creation.

I have checked the ase.py but it is not clear to me how to run the dataset creation.
Thanks