src/transformers/training_args.py/TrainingArguments/to_dict
class TrainingArguments:    def to_dict(self):
        """
        Serializes this instance while replace `Enum` by their values (for JSON serialization support).
        """
        d = asdict(self)
        for k, v in d.items():
            if isinstance(v, Enum):
                d[k] = v.value
            if isinstance(v, list) and len(v) > 0 and isinstance(v[0], Enum):
                d[k] = [x.value for x in v]
        return d