recover from `transformers 4.34 refactored`

[victorlee0505]

this PR is for #154.

I believe PreTrainedTokenizer super().__init__(**kwargs) attempted to use get_vocab from LLM but self._llm = llm is not yet set, hence it can not access to the LLM.

So I move it down and it works now.

*force-pushed to change author