> For the complete documentation index, see [llms.txt](https://boinc-ai.gitbook.io/transformers/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://boinc-ai.gitbook.io/transformers/api/main-classes/auto-classes/extending-the-auto-classes.md).

# Extending the Auto Classes

Each of the auto classes has a method to be extended with your custom classes. For instance, if you have defined a custom class of model `NewModel`, make sure you have a `NewModelConfig` then you can add those to the auto classes like this:

Copied

```
from transformers import AutoConfig, AutoModel

AutoConfig.register("new-model", NewModelConfig)
AutoModel.register(NewModelConfig, NewModel)
```

You will then be able to use the auto classes like you would usually do!

If your `NewModelConfig` is a subclass of `~transformer.PretrainedConfig`, make sure its `model_type` attribute is set to the same key you use when registering the config (here `"new-model"`).

Likewise, if your `NewModel` is a subclass of [PreTrainedModel](https://huggingface.co/docs/transformers/v4.34.1/en/main_classes/model#transformers.PreTrainedModel), make sure its `config_class` attribute is set to the same class you use when registering the model (here `NewModelConfig`).


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