Use of the `__post_init__` method outside of a dataclass

The `JsonSchema` class defined in `outlines/types/dsl.py` contains a `__post_init__` method that runs `jsonschema.Draft7Validator.check_schema(json.loads(self.schema))` to ensure the json schema provided by the user is valid. However, as it's not a `dataclass`, this method is never run.