IndexError: Invalid key: 0 is out of bounds for size 0

I am trying to fine-tune llama2-7b model in GCP. The notebook I am using for this can be found here.

When I use the dataset (timdettmers/openassistant-guanaco) given in the example, the training gets successfully completed.
However when I use my own dataset which is in the same format as the example dataset, I get the below error (my dataset can be found here).

From the logs I can see that the files are being read correctly.

Thank you for you help.