Example of Protocol class in Mypy

mypy_example.py

from typing import Any, Union, Dict
from typing_extensions import TypedDict, Protocol


class FooMeta:

    meta = dict(a=1)


class BarMeta:
    def __init__(self):

        self.meta = dict(foo="bar")


class SupportsMeta(Protocol):

    meta: Dict[str, Any]


def frobnicate(obj: SupportsMeta, key: str) -> Any:

    value = obj.meta[key]

    return value


def main():

    foo = FooMeta()
    bar = BarMeta()
    bar2 = BarMeta()

    print(frobnicate(foo, "a"))
    print(frobnicate(bar, "foo"))
    print(frobnicate(bar2, "foo"))


if __name__ == "__main__":
    main()