Use of generics in requests typing

Currently the requests typing makes heavy use of unions. For example the parameter type is:
https://github.com/python/typeshed/blob/f99e8b0615182bb0f17d9d126019d8d72c207ab3/stubs/requests/requests/sessions.pyi#L97-L103

The issue with this approach is that the type system can't keep track of which type has been chosen for a given field. For example, running pyright on this code:

from requests import Session

session = Session()
session.params = {}
reveal_type(session.params)

Shows us that the type system immediately "forgets" that our parameters are definitely in a dictionary:

test.py:5:13 - information: Type of "session.params" is "dict[str | bytes | int | float, str | bytes | int | float | Iterable[str | bytes | int | float] | None]"
0 errors, 0 warnings, 1 information

If we could make Session (as well as other classes such as Request) generic over the parameter type (as well as other fields), then we could keep track of this kind of state. For example, it might look like:

session: Session[dict] = Session()

Beginne mit dem verlinkten Abschnitt in requests/requests/sessions.pyi um die Zeilen 97–103 und überprüfe anschließend, wie Session und Request typisiert sind. Verwende das bereitgestellte pyright-Beispiel, um zu beurteilen, ob generische Parametertypen nach einer Zuweisung spezifisch bleiben; abgeschlossen ist die Aufgabe, wenn das vorgeschlagene generische Design für die betroffenen Klassen konsistent definiert ist und die ausgewählten Feldtypen beibehält.