code: public Interval filterInterval(String columnId, int idx) {
          List<Interval> selected = columnSelectionMap.get(columnId);
          if (selected != null && !selected.isEmpty()) {
              for (Interval interval : selected) {
                  if (interval.getIndex() == idx) {
                      return interval;
                  }
              }
          }
          return null;
      }
docs: Get the current filter interval matching the specified index
  
  @param columnId The column identifier.
  @param idx The index of the interval
  @return The target interval matching the specified parameters or null if it does not exist.