Fix self referencial dataclasses

[rnag]

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.