import sys
from typing import Any, Protocol, runtime_checkable


class Concrete:
    def __init__(self, x):
        self._x = x

    @property
    def x(self):
        if self._x is None:
            raise RuntimeError(f'raised from {self}')
        return


def check(klass):
    isinstance(Concrete(0), klass)
    isinstance(Concrete(None), klass)


check(Concrete) # this is trivial

@runtime_checkable
class Proto1(Protocol):
    @property
    def x(self):
        ...

check(Proto1)


@runtime_checkable
class Proto2(Protocol):
    x: Any

check(Proto2)


if sys.version_info >= (3, 9):
    @runtime_checkable
    class Proto3(Protocol):
        @classmethod
        @property
        def x(cls):
            raise RuntimeError(f'raised from {cls}')

    check(Proto3)