Change how "additional_special_tokens" argument in the ".from_pretrained" method of the tokenizer is taken into account (#13056)

* add test

* add change in PretrainedTokenizerBase

* change Luke

* deactivate

* add the possibility to add additional special tokens for M2M100

* format

* add special test for canine

* proposed changes for mbart

* proposed changes for mbart50

* proposed changes for byt5

* proposed changes for canine

* proposed changes for t5

* test fast and slow

* remove comment

* remove comment

* add fast version for all tests

* replace break by continue

* add more comments

* add check to avoid duplicates

* remove comment

* format

* proposed change for wave2vec2

* reverse changes mbart

* uncomment

* format

src/transformers/tokenization_utils_base.py

@@ -1862,6 +1862,12 @@ class PreTrainedTokenizerBase(SpecialTokensMixin, PushToHubMixin):
             with open(special_tokens_map_file, encoding="utf-8") as special_tokens_map_handle:
                 special_tokens_map = json.load(special_tokens_map_handle)
             for key, value in special_tokens_map.items():
+                if key in kwargs and kwargs[key]:
+                    # This value has already been redefined by the kwargs
+                    # We keep this new value and ignore the one stored in the special_tokens_map_file
+
+                    continue
+
                 if isinstance(value, dict):
                     value = AddedToken(**value)
                 elif isinstance(value, list):