code: void onFilterChanged(@Observes DataSetFilterChangedEvent event) {
          DataSetFilter filterOp = event.getFilter();
          dataSetLookup.removeOperations(DataSetOpType.FILTER);
          if (filterOp != null) {
              dataSetLookup.addOperation(0,
                                         filterOp);
          }
          changeEvent.fire(new DataSetLookupChangedEvent(dataSetLookup));
      }
docs: DataSetFilterEditor events