Fix Python type error

[pokey]

Latest pylance version is giving me the following error:

Cannot access attribute "__class__" for class "type[DataclassInstance]"
  A property defined within a protocol class cannot be accessed as a class variable

Note that this solution came from a chat with chatgpt so I have no idea whether it's correct. Please review carefully. We really should have unit tests for this function

I did run local talon tests and all green, as well as tried cheatsheet

Checklist

• [-] I have added tests
• [-] I have updated the docs and cheatsheet
• [x] I have not broken the cheatsheet