code: public static <C extends Comparable> ImmutableRangeSet<C> of(Range<C> range) {
      checkNotNull(range);
      if (range.isEmpty()) {
        return of();
      } else if (range.equals(Range.all())) {
        return all();
      } else {
        return new ImmutableRangeSet<C>(ImmutableList.of(range));
      }
    }
docs: Returns an immutable range set containing the specified single range. If {@link Range#isEmpty()
  range.isEmpty()}, this is equivalent to {@link ImmutableRangeSet#of()}.