Functions should return None, return SomeType | None or SomeType . SomeType can be a tuple, but that tuple should always have the same number of arguments. Flags like calculate_cost(return_as_float=True) should not exist. If you must have multiple versions of the same function with slightly different return signatures, I should be able to access everything in a typesafe way. This either means there should be
@typing.overloaddecorators providing all the typesafe variants of the function- 1 function containing the core logic and a other functions that wraps it and does type conversion (Both should have type inference or type hints.)