def __add__(self, other):
        if isinstance(other, dict):
            new = type(self)()  # May be a subclass of dict.
            new.update(self)
            new.update(other)
            return new

Is there something I’m missing? To me it would be cleaner and more memory/time performant to just `self.update(other)` rather than having a third list instance at operation time. But that would really only apply if you have truly massive dicts.