I've got this error when running 03. NSynth (Audio Classification by Computing Spectrograms On-the-fly).ipynb.
It fails in the following cell:
batch_size = 64
instrument_family_pattern = r'(\w+)_\w+_\d+-\d+-\d+.wav$'
data = (AudioItemList
.from_folder(NSYNTH_AUDIO)
.filter_by_func(lambda fn: 'acoustic' in fn.name)
.split_by_folder()
.label_from_re(instrument_family_pattern)
.databunch(bs=batch_size, tfms=tfms))