I'm trying to create my own class that has IO capability.
The class instances would have names similar to file names, but specified at the moment of instance creation.
However when I try setting name field, mypy is protesting.

Here's the minimal repro:

from typing import AnyStr, IO
class MyIO(IO[AnyStr]):
    def __init__(self, name: str) -> None:
        self.name = name

mypy output:

Test.py: note: In member "__init__" of class "MyIO":
Test.py:5: error: Property "name" defined in "IO" is read-only