KeyError: 'n01440764' at SplitData.split_by_func(il, partial(grandparent_splitter, valid_name='val'))

I’m getting this error when i try to execute the 09_optimizers.ipynb notebook.
The problem is at this line:
sd = SplitData.split_by_func(il, partial(grandparent_splitter, valid_name=‘val’))

Could someone please help?