Consider adding a "TopLevel" keyword that stands in for the top level bound of a corresponding type variable

Summary

Please consider a new typing keyword that stands in for the top level type of a corresponding type variable.

Motivation

Consider a test here and the corresponding definition of DistributionInfo here. The test loses all typing information because I used DistributionInfo[Any, Any, Any]. So if I want typing information, I have to use:

def test_flatten(generator: Generator,
                 distribution_info: DistributionInfo[NaturalParametrization[ExpectationParmetrization, JaxComplexArray],
                                                     ExpectationParametrization[NaturalParmetrization],
                                                     NumpyComplexArray]) -> None:

I would much rather just do

def test_flatten(generator: Generator,
                 distribution_info: DistributionInfo[TopLevel, TopLevel, TopLevel]) -> None:

It's not just shorter, but it reduces churn if the type definitions change. Note that TopLevel is recursive (it chooses the top level of the nested types too).

Comienza con los tests vinculados tests/test_flatten.py y tests/distribution_info.py para entender qué información de tipos se pierde cuando se usa DistributionInfo[Any, Any, Any]. Aclara la semántica recursiva prevista de TopLevel y en qué se diferencia del comportamiento existente de las variables de tipo. Se considerará terminado cuando la propuesta incluya una especificación precisa y un proceso de validación acordado.