that way, you can do something like: ``` current_exception = sys.exception() if current_exception is not None: tb = traceback_with_variables.format_exc(current_exception) ``` instead of currently needing to do ``` current_exception = sys.exception() if current_exception is not None: tb = traceback_with_variables.format_exc(cast(current_exception, Exception)) ``` and have the type checker be happy. this makes sense more generally because there's no reason eg a `KeyboardInterrupt` shouldn't be handled with this library, right?