Update: add type hints to check_tokenizers.py
Author: ajeet214
Pull request: yes

chore(typing): add type hints to scripts/check_tokenizers.py and use PreTrainedTokenizerBase

# What does this PR do?
Adds lightweight type hints to `scripts/check_tokenizers.py`:

- Annotate params/returns for helper functions: `check_diff`, `check_LTR_mark`, `check_details`, `test_string`, `test_tokenizer`
- Uses `transformers.tokenization_utils_base.PreTrainedTokenizerBase` for `slow`/`fast` instead of `Any`
- Make `check_LTR_mark` return `bool` explicitly (no behavior change)

This improves readability, IDE support, and static analysis (mypy/pyright) without changing runtime behavior.

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Fixes # (issue)


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Comments:
LGTM but slightly confused about the `Any` types - is there a reason we can't import a base tokenizer class here?

> LGTM but slightly confused about the `Any` types - is there a reason we can't import a base tokenizer class here?

@Rocketknight1, Thanks for the suggestion! I’ve updated the annotations to use `transformers.tokenization_utils_base.PreTrainedTokenizerBase` instead of `Any`. This base class covers both `PreTrainedTokenizer` and `PreTrainedTokenizerFast` and exposes all methods used in this script (`encode`, `decode`, `encode_plus`, `tokenize`).

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_40094). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.