docs: protected void checkNumberOfParents(List<S> population, int numberOfParentsForCrossover) {
      if ((population.size() % numberOfParentsForCrossover) != 0) {
        throw new JMetalException("Wrong number of parents: the remainder if the " +
                "population size (" + population.size() + ") is not divisible by " +
                numberOfParentsForCrossover) ;
      }
    }