code: public static <T> ItemsSketch<T> getInstance(final Comparator<? super T> comparator) {
      return getInstance(PreambleUtil.DEFAULT_K, comparator);
    }
docs: Obtains a new instance of an ItemsSketch using the DEFAULT_K.
  @param <T> type of item
  @param comparator to compare items
  @return a GenericQuantileSketch