def off(self, event=None, *handlers):

        if not event:
            self.events.clear()
            return True

        if not event in self.events:
            raise EventNotFound(event)

        if not handlers:
            self.events.pop(event, None)
            return True

        for callback in handlers:
            if not callback in self.events[event]:
                raise HandlerNotFound(event, callback)
            while callback in self.events[event]:
                self.events[event].remove(callback)
        return True
Checks that the given string is a valid two-letter U.S. state abbreviation
dataset/ETHPy150Open timofurrer/pyobservable/observable/core.py/Observable.off--crossover with--dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-0.96/django/core/validators.py/isValidUSState