prohibit specifying computeds that type doesn't have declared

[1st1]

MyType.select(computed=...) should be prohibited at the type level if MyType doesn't have computed. We won't be able to unpack fields we don't have definitions for, so we have to simply reject this at the typing level.

[elprans]

@1st1, I'm not sure there is a way to achieve this at the typing level currently. We generate the signature for select in generated models, there is no general way of "transplanting" class annotations onto an arbitrary method signature (@dataclass_transform is special and hardcoded to __init__). Something to address in a typing PEP.

[1st1]

We can't do this with the current typing

[1st1]

Do this at runtime