22_tutorial.imagenette in fastai repo giving an error in pytorch_adamw

In this tutorial the section “Changing the optimizer” explains pytorch_adamw, I was running this exact notebook in Google Colab pro. After creating the learner when you run learn.lr_find() then I received.

TypeError: __init__() missing 1 required positional argument: 'opt'
(i.e., the in the constructor of OptimWrapper class.)

The same error has occurred again in

for the next topic in the tutorial which is

Changing the training loop with a Callback

Can somebody please explain how to correct the error? Thanks!!

I changed the definition of the function pytorch_adamw from-

def pytorch_adamw(param_groups, **kwargs):
    return OptimWrapper(torch.optim.AdamW([{'params': ps, **kwargs} for ps in param_groups]))


def pytorch_adamw(param_groups, **kwargs):
    return OptimWrapper([{'params': ps, **kwargs} for ps in param_groups], torch.optim.SGD)

and now it is working fine in colab pro. Because as suggested in the error msg, the constructor of OptimWrapper was expecting a second positional argument, which is an optimizer, so I provided the
torch.optim.SGD as the second positional parameter. while the first positional parameter is an iterable.

What am I missing?

The error was occurring because of this.
The constructor signature of OptimWrapper has changed.

OptimWrapper now has a different constructor signature, which makes it easier to wrap PyTorch optimizers.

therefore the corresponding code can be changed as follows.
@delegates(torch.optim.AdamW.init )
def pytorch_adamw(param_groups, **kwargs):
return OptimWrapper([{‘params’: ps, **kwargs} for ps in param_groups], torch.optim.AdamW )