code: public PeriodFormatterBuilder appendSuffix(String text) {
          if (text == null) {
              throw new IllegalArgumentException();
          }
          return appendSuffix(new SimpleAffix(text));
      }
docs: Append a field suffix which applies only to the last appended field. If
  the field is not printed, neither is the suffix.
  
  @param text text to print after field only if field is printed
  @return this PeriodFormatterBuilder
  @throws IllegalStateException if no field exists to append to
  @see #appendPrefix