docs: private Map<String, Object> generateEmptyEventsFromAggregators(Map<String, AggregatorFactory> aggMap,
                                                                   Map<String, PostAggregator> postAggMap)
    {
      Map<String, Object> emptyEvents = new LinkedHashMap<>();
      aggMap.values().forEach(agg -> {
        Aggregator aggFactorized = agg.factorize(getEmptyColumnSelectorFactory());
        emptyEvents.put(agg.getName(), aggFactorized.get());
      });
      postAggMap.values().forEach(postAgg -> emptyEvents.put(postAgg.getName(), postAgg.compute(emptyEvents)));
      return emptyEvents;
    }