def register(self, key, value, exist_ok=False):
        """
        Register a new configuration in this mapping.
        """
        if key in self._mapping.keys() and not exist_ok:
            raise ValueError(f"'{key}' is already used by a Transformers config, pick another name.")
        self._extra_content[key] = value

        Register a new configuration in this mapping.
        
dpkd/transformers/src/transformers/models/auto/configuration_auto.py