How should I type my validators?

I'm trying to add some types to some attrs-using code that uses validators.

Here's a minimal example of such:

from typing import Any, TypeVar

from attr import Attribute

T = TypeVar("T")


def my_validator(instance: Any, attribute: Attribute[T], value: T) -> Any:
    pass

The type is derived by looking at attr/validators.pyi and attr/__init__.pyi.

The code type-checks fine, but fails to execute:

jml@hope:~
$ mypy --strict attribute.py
jml@hope:~
$ python attribute.py
Traceback (most recent call last):
  File "attribute.py", line 8, in <module>
    def my_validator(instance: Any, attribute: Attribute[T], value: T) -> Any:
TypeError: 'type' object is not subscriptable

If I remove the [T], the opposite happens:

jml@hope:~
$ mypy --strict attribute.py
attribute.py:8: error: Missing type parameters for generic type
jml@hope:~
$ python attribute.py

What type should my validators have?

Start by comparing the generic declarations in attr/validators.pyi and attr/init.pyi with the runtime Attribute behavior shown by attribute.py. Run both mypy --strict attribute.py and python attribute.py; done means validators have types that satisfy strict checking without raising the reported runtime TypeError.