TypeError: non-default argument 'value' follows default argument

I'm trying to inherit from a dataclass with an optional id in the parent, however, I am seeing `TypeError: non-default argument 'value' follows default argument`. This is the minimal code to reproduce.
```
from typing import Optional
import chex

@chex.dataclass
class Base:
idx: Optional[int] = None

@chex.dataclass
class Derived(Base):
value: int
```
This is an issue with the `dataclasses` library rather than `chex.dataclasses`, however, according to https://stackoverflow.com/questions/51575931/class-inheritance-in-python-3-7-dataclasses#answer-69822584, it is possible to fix by setting `kw_only=True`.