Add unit tests for tuning/data/tokenizer_data_utils.py

[tedhtchang]

Is your feature request related to a problem? Please describe.

Add unit tests for the tuning/data/tokenizer_data_utils.py module.

Describe the solution you'd like

If possible, each function should have test cases in the file tests/data/test_tokenizer_data_utils.py
and pass test with the command pytest tests/data/test_tokenizer_data_utils.py

Describe alternatives you've considered

A clear and concise description of any alternative solutions or features you've considered.

Additional context

Add any other context about the feature request here.

[Ssukriti]

lower priority- can be in backlog