docs: private PeriodFormatterBuilder appendSuffix(PeriodFieldAffix suffix) {
          final Object originalPrinter;
          final Object originalParser;
          if (iElementPairs.size() > 0) {
              originalPrinter = iElementPairs.get(iElementPairs.size() - 2);
              originalParser = iElementPairs.get(iElementPairs.size() - 1);
          } else {
              originalPrinter = null;
              originalParser = null;
          }
  
          if (originalPrinter == null || originalParser == null ||
                  originalPrinter != originalParser ||
                  !(originalPrinter instanceof FieldFormatter)) {
              throw new IllegalStateException("No field to apply suffix to");
          }
  
          clearPrefix();
          FieldFormatter newField = new FieldFormatter((FieldFormatter) originalPrinter, suffix);
          iElementPairs.set(iElementPairs.size() - 2, newField);
          iElementPairs.set(iElementPairs.size() - 1, newField);
          iFieldFormatters[newField.getFieldType()] = newField;
          
          return this;
      }