code: public HashMap<StreamShardMetadata, SequenceNumber> snapshotState() {
  		// this method assumes that the checkpoint lock is held
  		assert Thread.holdsLock(checkpointLock);
  
  		HashMap<StreamShardMetadata, SequenceNumber> stateSnapshot = new HashMap<>();
  		for (KinesisStreamShardState shardWithState : subscribedShardsState) {
  			stateSnapshot.put(shardWithState.getStreamShardMetadata(), shardWithState.getLastProcessedSequenceNum());
  		}
  		return stateSnapshot;
  	}
docs: Creates a snapshot of the current last processed sequence numbers of each subscribed shard.
  
  @return state snapshot