## The problem
With plaid-python 8.0.0b12, `client.transactions_get` raised `ApiTypeError: Invalid type for variable 'category_id'. Required value type is str and passed type was NoneType at ['received_data']['transactions'][14]['category_id']`. Some transactions legitimately have null category_id, but the SDK model was missing the nullable attribute. Passing `_check_return_type=False` just moved the failure to `.to_dict()` with `AttributeError: 'dict' object has no attribute '_composed_schemas'`.
## The fix
A maintainer confirmed the category_id field was erroneously missing `nullable` in the spec and fixed it on Plaid's side, shipping the corrected SDK in 8.0.0b13. Fix: upgrade plaid-python to 8.0.0b13+. Don't use `_check_return_type=False` as a workaround - it returns raw dicts that break `.to_dict()` with an AttributeError about `_composed_schemas`.