presto-main/src/main/java/io/prestosql/operator/aggregation/multimapagg/LegacyGroupedMultimapAggregationState.java/LegacyGroupedMultimapAggregationState/forEach
class LegacyGroupedMultimapAggregationState:    @Override
    public void forEach(MultimapAggregationStateConsumer consumer)
    {
        BlockBuilder keyBlockBuilder = keyBlockBuilders.get(getGroupId());
        BlockBuilder valueBlockBuilder = valueBlockBuilders.get(getGroupId());
        if (keyBlockBuilder == null) {
            return;
        }
        for (int i = 0; i < keyBlockBuilder.getPositionCount(); i++) {
            consumer.accept(keyBlockBuilder, valueBlockBuilder, i);
        }
    }