def off(self, event=None, *handlers):
        """unregister an event or handler from an event"""

        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 not in self.events[event]:
                self.events[event].remove(callback)
        return True
dataset/ETHPy150Open timofurrer/pyobservable/observable/core.py/Observable.off/operator `in` -> `not in`