basic-lib/src/main/java/com/streamsets/pipeline/stage/processor/aggregation/aggregator/AggregatorDataProvider.java
public AggregatorData getData(Aggregator aggregator) {
    Utils.checkState(started, "Not started");
    Utils.checkState(!stopped, "Already stopped");
    Utils.checkNotNull(aggregator, "aggregator");
    Utils.checkArgument(
        aggregators.contains(aggregator),
        Utils.formatL("Aggregator {} is not registered to provider", aggregator)
    );
    return data.get(aggregator);
  }
public AggregatorData getData(Aggregator aggregator) {
    Utils.checkState(started, "Not started");
    Utils.checkState(!stopped, "Already stopped");
    Utils.checkNotNull(aggregator, "aggregator");
    Utils.checkArgument(
        aggregators.contains(aggregator),
        Utils.formatL("Aggregator {} is not registered to provider", aggregator)
    );
    return data.get(aggregator);
  }
Returns the current AggregatorData for an Aggregator.
<p/>
This method is also used by the group-by element Aggregators.

@param aggregator Aggregator to get the AggregatorData for.
@return the current AggregatorData for an Aggregator.