docs: @Override
      public List<ColumnDescription> getColumnDescriptions(
              TitleAndCount[] items, boolean showAll, BaseReportForm form) {
          String description = null;
          int multipleValues = 0;
          for (TitleAndCount item : items) {
              if (item.getCriteriaValuesSelected() > 1 || showAll) {
                  multipleValues++;
                  description =
                          description == null
                                  ? item.getCriteriaItem()
                                  : description + displaySeparator + item.getCriteriaItem();
              }
          }
          // If all items have 1 value selected or if there is only 1 item, make the
          // first item the column descriptor.
          if (multipleValues == 0 || items.length == 1) {
              description = items[0].getCriteriaItem();
          }
  
          final List<ColumnDescription> columnDescriptions = new ArrayList<ColumnDescription>();
          columnDescriptions.add(new ColumnDescription(description, ValueType.NUMBER, description));
          return columnDescriptions;
      }