Normalize function for batches

I am trying to normalize my images to train cifar

I have my batch_tfms defined as:

batch_tfms = [Dihedral(),Normalize.from_stats(*cifar_stats)]

when I run my dataloader from a notebook I get:

Could not do one pass in your dataloader, there is something wrong in it

but if I set my batch_tfms as

batch_tfms = [Dihedral(),Normalize()]

it works…

My dataloader is defined as:

dls = ImageDataLoaders.from_folder(cifar10, train='train', 
                                   valid='test', device=1,