@Override
  public String allowDeleteDataElementCategoryCombo(DataElementCategoryCombo categoryCombo) {
    Collection<CaseAggregationCondition> conditions =
        aggregationConditionService.getAllCaseAggregationCondition();

    for (CaseAggregationCondition condition : conditions) {
      if (categoryCombo.getOptionCombos().contains(condition.getOptionCombo())) {
        return ERROR;
      }
    }

    return null;
  }