def pre_save(self, model_instance, add):
        value = now()
        previous = getattr(model_instance, self.monitor_attname, None)
        current = self.get_monitored_value(model_instance)
        if previous != current:
            if self.when is None or self.when in current:
                setattr(model_instance, self.attname, value)
                self._save_initial(model_instance.__class__, model_instance)
        return super(MonitorField, self).pre_save(model_instance, add)
dataset/ETHPy150Open carljm/django-model-utils/model_utils/fields.py/MonitorField.pre_save/swapped operands of `in`