Use _BaseAutoModelClass's register method
diff --git a/src/transformers/models/auto/auto_factory.py b/src/transformers/models/auto/auto_factory.py
index d322f83668ea1..5519d82e7aabf 100644
--- a/src/transformers/models/auto/auto_factory.py
+++ b/src/transformers/models/auto/auto_factory.py
@@ -418,7 +418,7 @@ def from_config(cls, config, **kwargs):
             else:
                 repo_id = config.name_or_path
             model_class = get_class_from_dynamic_module(class_ref, repo_id, **kwargs)
-            cls._model_mapping.register(config.__class__, model_class, exist_ok=True)
+            cls.register(config.__class__, model_class, exist_ok=True)
             _ = kwargs.pop("code_revision", None)
             return model_class._from_config(config, **kwargs)
         elif type(config) in cls._model_mapping.keys():
@@ -477,7 +477,7 @@ def from_pretrained(cls, pretrained_model_name_or_path, *model_args, **kwargs):
                 class_ref, pretrained_model_name_or_path, **hub_kwargs, **kwargs
             )
             _ = hub_kwargs.pop("code_revision", None)
-            cls._model_mapping.register(config.__class__, model_class, exist_ok=True)
+            cls.register(config.__class__, model_class, exist_ok=True)
             return model_class.from_pretrained(
                 pretrained_model_name_or_path, *model_args, config=config, **hub_kwargs, **kwargs
             )

# What does this PR do?
Switching `_BaseAutoModelClass`'s `from_pretrained` and `from_config` to use the register classmethod that it defines rather than using the `_LazyAutoMapping` register method directly. This makes use of the additional consistency check within `_BaseAutoModelClass`'s register method.


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## Before submitting
- [ ] Did you read the [contributor guideline](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md#start-contributing-pull-requests),
      Pull Request section? Yes
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## Who can review?

Anyone in the community is free to review the PR once the tests have passed. @sgugger

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