docs: public static <E> Distribution<E> laplaceWithExplicitUnknown(Counter<E> counter, double lambda, E UNK) {
      Distribution<E> norm = new Distribution<E>();
      norm.counter = new ClassicCounter<E>();
      double total = counter.totalCount() + (lambda * (counter.size() - 1));
      norm.numberOfKeys = counter.size();
      norm.reservedMass = 0.0;
      for (E key : counter.keySet()) {
        if (key.equals(UNK)) {
          norm.counter.setCount(key, counter.getCount(key) / total);
        } else {
          norm.counter.setCount(key, (counter.getCount(key) + lambda) / total);
        }
      }
      return norm;
    }