code: public List<Integer> filterIndexes(String columnId) {
          List<Integer> result = new ArrayList<>();
          List<Interval> selected = columnSelectionMap.get(columnId);
          if (selected == null) {
              return result;
          }
          for (Interval interval : selected) {
              result.add(interval.getIndex());
          }
          return result;
      }
docs: Get the current filter selected interval indexes for the given data set column.
  
  @param columnId The column identifier.
  @return A list of interval indexes