ContinuousFeed NameError during unmarshalling of SourceResponse

First let me apologise for the lack of specificity atm. I'm writing this at the end of my work day after I worked around the issue, so I'm writing this from memory. I do hope to come back and fill in some details, provide proper code, etc, but I may be told to focus my time/energy elsewhere now that our code is working again(🙄) 🙏

Using version 0.50.1, I encountered a NameError in the `sources.get_source` call, and traceback took me through `utils.unmarshal_json` to the `unmarshal.from_dict` call (and then into dataclasses_json library).
It seems to be choking on the `models.SourceE2eTestCloud` use in `models.SourceConfiguration`, as the NameError mentions that `ContinuousFeed` cannot be found (?, apologies, I've forgotten the exact message).