Class Vec2D

Lib/test/test_typing.py:4677–4682

    def test_protocol_issubclass_error_message(self):
        @runtime_checkable
        class Vec2D(Protocol):
            x: float
            y: float

            def square_norm(self) -> float:
                return self.x ** 2 + self.y ** 2

        self.assertEqual(Vec2D.__protocol_attrs__, {'x', 'y', 'square_norm'})
        expected_error_message = (