def test_should_return_just_when_binding_just_given_function_returning_just():
just_one = Just(1)
just_add_one: Callable[[int], Maybe[int]] = lambda to_sum: Just(to_sum + 1)
assert just_one.bind(just_add_one) == Just(2)
assert just_one | just_add_one == Just(2)
def test_should_return_nothing_when_binding_just_given_function_returning_nothing():
just_one = Just(1)
make_nothing: Callable[[int], Maybe[int]] = lambda _: Nothing()
assert just_one.bind(make_nothing) == Nothing()
assert just_one | make_nothing == Nothing()