code: @NotNull
      public ComparatorCompat<T> thenComparingLong(@NotNull ToLongFunction<? super T> keyExtractor) {
          return thenComparing(comparingLong(keyExtractor));
      }
docs: Adds the comparator, that uses a function for extract
  a {@code long} sort key, to the chain.
  
  @param keyExtractor  the function that extracts the sort key
  @return the new {@code ComparatorCompat} instance