I feel like this proposal is not quite right, but maybe the idea will provoke some thoughts about something similar that -would- be right. The idea first came to me upon realizing that since `namedtuple` classes have no special base class beyond `tuple`, there should be some way of identifying them as being primarily structural, even though they are instances of `tuple` which, in other cases, usually means something that is primarily sequential. It is easily possible to identify a namedtuple by checking to see whether it has an `_asdict` method, but it might be nice to formalize the way that struct-like objects are identified in a virtual base class and be something that had application beyond just checking whether a `tuple` is a `namedtuple`.