`Model.update()` signature needs love

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Currently:

We want the signature to be as short as possible in the IDE

        Something[str]=GoodName
        str | Unset=unset
        str | Unspecified=unspecified   # we have a winner!
        str | NotPassed=not_passed
        str | Unspec=unspec

[1st1]

In general this applies to everything - review other generated methods.

[1st1]

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