dataset = dataset.train_test_split(test_size=0.1)

Data collator
In order to combine multiple examples into a batch, you need to define a custom data collator. This collator will pad shorter sequences with padding 
tokens, ensuring that all examples have the same length. For the spectrogram labels, the padded portions are replaced with the special value -100. This special value 
instructs the model to ignore that part of the spectrogram when calculating the spectrogram loss.