def METHOD_NAME(
    study: Study,
    parent_population: Sequence[FrozenTrial],
    rng: np.random.RandomState,
    dominates: Callable[[FrozenTrial, FrozenTrial, Sequence[StudyDirection]], bool],
) -> FrozenTrial:
    population_size = len(parent_population)
    candidate0 = parent_population[rng.choice(population_size)]
    candidate1 = parent_population[rng.choice(population_size)]
    # TODO(ohta): Consider crowding distance.
    if dominates(candidate0, candidate1, study.directions):
        return candidate0
    else:
        return candidate1