Shared via mypy Playground

main.py

from typing import TypeVar
from abc import ABC

class A(ABC):
    def m(self) -> None:
        print("A")
        
class B(A):
    def m(self) -> None:
        print("B")
        
class C(A):
    def m(self) -> None:
        print("C")
        
T = TypeVar("T", bound=A)    
    
ls: list[T] = [B(), C()]