How do I correctly add type-hints to Mixin classes?

For reference, mypy recommends to implement mixins through a Protocol (documentation here).

It works with mypy >= 750.

from typing import Protocol


class HasValueProtocol(Protocol):
    @property
    def value(self) -> int: ...


class MultiplicationMixin:

    def multiply(self: HasValueProtocol, m: int) -> int:
        return self.value * m


class AdditionMixin:

    def add(self: HasValueProtocol, b: int) -> int:
        return self.value + b


class MyClass(MultiplicationMixin, AdditionMixin):

    def __init__(self, value: int) -> None:
        self.value = value

The Protocol base class is provided in the typing_extensions package for Python 2.7 and 3.4-3.7.