How about supporting Unigram tokenizer in NeMO?
Currently NeMo has BPE but I don't see Unigram.

[Unigram is better than BPE.](https://arxiv.org/pdf/2004.03720.pdf)

[SpeechBrain supports Unigram.](https://colab.research.google.com/drive/12yE3myHSH-eUxzNM0-FLtEOhzdQoLYWe?usp=sharing)