adt_boolean_example.py

from abc import ABC, abstractmethod
from dataclasses import dataclass


class Bool(ABC):
    @abstractmethod
    def __bool__(self):
        """True/False depends on the type"""

@dataclass
class Truthy(Bool):
    def __bool__(self):
        return True


@dataclass
class Falsy(Bool):
    def __bool__(self):
        return False


def test_true_and_false():
    assert bool(Truthy()) is True
    assert bool(Falsy()) is False