Fix self referencial dataclasses

case when

```
class A:
  b: B

class B:
  a: A
```

As an example.

My theory is that `cls_fromdict` is generated for class `A` twice, because of self-reference. I need to do some tests to confirm this is the case, and if so need to do a check when storing parser for `A`, so we only generate and store it once, if that's possible.