Is there any way to handle variable-length sequences and train TCN models on them ([the LSTM in PyTorch](https://pytorch.org/docs/stable/generated/torch.nn.utils.rnn.pack_padded_sequence.html) and also [the Keras implementation of TCN](https://github.com/philipperemy/keras-tcn/blob/master/tasks/multi_length_sequences.py) can handle variable-length sequences)?