[Python] How Do I Open A File in a Subclass of BufferedIOBase in Python

I want to create my own reader class that is derived from BufferedIOBase. I'd like to have multiple 'open' class methods with differing parameters to create class instances, like this:

from __future__ import annotations

import io

class MyReader(io.BufferedIOBase):

@classmethod
def open1(cls, filename:str) -> MyReader:
r = MyReader()
# How do I open 'r'?
return r

@classmethod
def open2(cls, buffer:bytes) -> MyReader:
...

def __init__(self):
super().__init__()

with MyReader.open("filename") as reader:
reader.read()


How do I actually open the file in my class? The can't use "r = open(...)" in place of "r = MyReader()" because that won't create a "MyReader" object; and there's no available method in the MyReader class and its superclasses to do an open.

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