Hello!

Came across this kata and was happy to train it, thanks for the python translation!

However, I'd like to make a proposal to add the following exception definition to the Solution setup as its absence might be a bit misleading and it doesn't seem to be related to the kata main point (the decorator usage).

class UnexpectedTypeException(Exception):
    """Exception to be raised when function returns an object of invalid type."""
    pass

Also, there is still an InvalidTypeException mentioned in the Sample test cases section. Seems like a copy-paste leftover ;)