in flink-connector-gcp-pubsub/src/main/java/org/apache/flink/streaming/connectors/gcp/pubsub/common/AcknowledgeOnCheckpoint.java [113:116]
public void restoreState(List<AcknowledgeIdsForCheckpoint<ACKID>> state) {
outstandingAcknowledgements = new AtomicInteger(numberOfAcknowledgementIds(state));
acknowledgeIdsPerCheckpoint = state;
}