[Python] How to use python generic hints to indicate value type in parent class?

I have a static member that will be some implementation of ToolInterface interface. I inherit the class that has that member and want to specify what implementation is used.

I tried this:

tool_test_base.py


from typing import Generic, TypeVar

from abstract_tool import ToolInterface


TToolImpl = TypeVar("TToolImpl", ToolInterface)

class ToolTestBase(Generic[TToolImpl]):

tool_impl = None # type: TToolImpl

@test_case
test_do_something(self):
assert self.tool_impl.do_something() == "hello"

abstract_tool.py


def ToolInterface:
def do_something():
assert False, "Tool method not implemented"


Now I have a class that extends the tool test and also provides a specific implementation:

my_tool.py


from abstract_tool import ToolInterface
class MyTool(ToolInterface):
do_something(self):
return "hello"
do_something_special(self):
return ""


my_tool_test.py


from tool_test_base import ToolTestBase
from my_tool import MyTool

class MyToolTest(ToolTestBase[MyTool]):
test_something_special(self):
assert self.tool_impl.do_something_special() == ""


Now by writing ToolTestBase[MyTool] I was hoping to indicate that TToolImpl is MyTool and not MyToolBase. However, it is not working as intended. I see tool_impl hints for MyToolBase but not for MyTool

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