attempt to use pep-646 variadic generics for Row, Result, select(), others

[zzzeek]

it's only in Python 3.10, the ability to make our own types that are like tuples:

https://www.python.org/dev/peps/pep-0646/

what we would want is:

stmt: Select[User, str, int]  = select(User, Address.name, Address.id).join_from(User, Address)

result: Result[User, str, int] = session.execute(stmt)

for row: Row[User, str, int] in result:
    # ...

that is, every ReturnsRows class as well as Result and Row become some kind of covariant variadic generic. is that every word ?

[zzzeek]

here's from the original discussion for pep 646: python/typing#193 (comment)

[zzzeek]

superseded by sqlalchemy/sqlalchemy#7516 for 2.0

[CaselIT]

we could have transferred it. In any case I think we can just close this