Repository: huggingface/transformers
Pull request: Fix `KeyError` when patching mistral regex

# What does this PR do?

Seems like the same `fix_mistral_regex` is provided multiple times, replacing `get` with `pop` to avoid running into `KeyError` fixes the issue.
```
  File "/mambaforge/envs/cf/lib/python3.10/site-packages/transformers/models/auto/processing_auto.py", line 400, in from_pretrained
    return PROCESSOR_MAPPING[type(config)].from_pretrained(pretrained_model_name_or_path, **kwargs)
  File "/mambaforge/envs/cf/lib/python3.10/site-packages/transformers/processing_utils.py", line 1413, in from_pretrained
    args = cls._get_arguments_from_pretrained(pretrained_model_name_or_path, processor_dict, **kwargs)
  File "/mambaforge/envs/cf/lib/python3.10/site-packages/transformers/processing_utils.py", line 1525, in _get_arguments_from_pretrained
    tokenizer = cls._load_tokenizer_from_pretrained(
  File "/mambaforge/envs/cf/lib/python3.10/site-packages/transformers/processing_utils.py", line 1474, in _load_tokenizer_from_pretrained
    tokenizer = auto_processor_class.from_pretrained(
  File "/mambaforge/envs/cf/lib/python3.10/site-packages/transformers/models/auto/tokenization_auto.py", line 700, in from_pretrained
    return tokenizer_class.from_pretrained(pretrained_model_name_or_path, *inputs, **kwargs)
  File "/mambaforge/envs/cf/lib/python3.10/site-packages/transformers/tokenization_utils_base.py", line 1757, in from_pretrained
    return cls._from_pretrained(
  File "/mambaforge/envs/cf/lib/python3.10/site-packages/transformers/tokenization_utils_base.py", line 2009, in _from_pretrained
    tokenizer = cls(*init_inputs, **init_kwargs)
  File "/mambaforge/envs/cf/lib/python3.10/site-packages/transformers/models/gemma/tokenization_gemma.py", line 99, in __init__
    super().__init__(
  File "/mambaforge/envs/cf/lib/python3.10/site-packages/transformers/tokenization_utils_tokenizers.py", line 373, in __init__
    self._tokenizer = self._patch_mistral_regex(
KeyError: 'fix_mistral_regex'
```

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Changed files:
filename: src/transformers/tokenization_utils_tokenizers.py
patch: @@ -456,7 +456,7 @@ def __init__(self, *args, **kwargs):
                 self._tokenizer,
                 self.init_kwargs.get("name_or_path", None),
                 init_kwargs=self.init_kwargs,
-                fix_mistral_regex=kwargs.get("fix_mistral_regex"),
+                fix_mistral_regex=kwargs.pop("fix_mistral_regex", None),
                 **kwargs,
             )
 

filename: tests/models/auto/test_tokenization_auto.py
patch: @@ -300,6 +300,12 @@ def test_auto_tokenizer_from_local_folder_mistral_detection(self):
         self.assertIsInstance(tokenizer2, tokenizer.__class__)
         self.assertTrue(tokenizer2.vocab_size > 100_000)
 
+    def test_auto_tokenizer_from_mistral_patching(self):
+        """See #43376, regression when kwarg is manually passed to patch the regex in mistral tokenizers"""
+        AutoTokenizer.from_pretrained(
+            "mistralai/Ministral-3-3B-Instruct-2512", fix_mistral_regex=True
+        )  # should not error
+
     @require_tokenizers
     def test_auto_tokenizer_loads_bloom_repo_without_tokenizer_class(self):
         tokenizer = AutoTokenizer.from_pretrained("trl-internal-testing/tiny-BloomForCausalLM")