The check to see whether the passed-in mode parameter was a valid member of the enum was incorrect (at least until Python 3.12), due to a leftover from the implementation before the mode was implemented as an enum. This was causing a TypeError inside `__contains__`, since that can't check for values, only instances. This change updates it to attempt to construct a `Mode` enum from the value, and catching the error if it's not a correct value. Testing Done: - Verified that new try/except was the correct way to handle this. - Ran unit tests.