Repository: huggingface/transformers
Pull request: [Fix] Add missing init_kwargs to MistralCommonBackend for v5 processor compatibility

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This PR fixes a bug in `MistralCommonBackend` (introduced in v5) where the `init_kwargs` attribute was missing. This caused crashes when using the tokenizer with processors like `PixtralProcessor`, which rely on this attribute to merge configurations.

Specifically, it adds the manual initialization of `self.init_kwargs` in `MistralCommonBackend.__init__`.

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Fixes #43110 
Please refer to [Related vLLM issue](https://github.com/vllm-project/vllm/issues/31792#issuecomment-3717160427) for the error traceback.

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Changed files:
filename: src/transformers/tokenization_mistral_common.py
patch: @@ -268,6 +268,15 @@ def __init__(
         if kwargs and not set(kwargs.keys()).issubset(_VALID_INIT_KWARGS):
             raise ValueError(f"Kwargs {list(kwargs.keys())} are not supported to init `MistralCommonBackend`.")
 
+        self.init_kwargs = {
+            "tokenizer_path": tokenizer_path,
+            "mode": mode,
+            "model_max_length": model_max_length,
+            "padding_side": padding_side,
+            "truncation_side": truncation_side,
+            "model_input_names": model_input_names,
+            "clean_up_tokenization_spaces": clean_up_tokenization_spaces,
+        }
         self._tokenizer_path = Path(tokenizer_path)
         self._mode = self._get_validation_mode(mode)