What is the proper way to do this code, so a linter does not see an error?

lint_example.py

from typing import Iterable
from typing import TypeVar
from typing import Generic

"""
This is the API section. 
The user should not be changing this part of the code.
"""


class MyAPIParentClass:
    def f(self):
        print("F")


T = TypeVar('T', bound=MyAPIParentClass)


class MyClassList(Generic[T]):
    def __init__(self):
        self.my_list = []

    def append(self, item: MyAPIParentClass):
        self.my_list.append(item)

    def __iter__(self) -> Iterable[T]:
        return iter(self.my_list)


"""
This is the user code section.
The users creates a class to extend the API.
The user is creating a custom class to extend the base MyAPIParentClass
and using the APIs MyClassList to hold the instances.
"""


class MyCustomChildClass(MyAPIParentClass):
    def g(self):
        print("G")


def main():
    # Create instances of my derived class
    my_list: MyClassList[MyCustomChildClass] = MyClassList()

    # Add them to the list
    for i in range(10):
        new_item = MyCustomChildClass()
        my_list.append(new_item)

    # Now call my custom function. It works, but linting will error out
    # because it doesn't know this is an instance of MyCustomChildClass, just
    # MyParentClass.
    # In C++ I'd use a cast to tell the compiler it was MyCustomChildClass.
    # What am I supposed to do here?
    for my_item in my_list:
        my_item.g()

main()

@vlasovskikh I think I'm looking for version #1 of your answer.

Version #2 will still cause the linter to be unhappy.

I took what you said and updated the example. The linter seems happy. At least with the call to g(). Let me know if there's a better way to code it than version 2 of the example here. Thanks.