private byte[] writeToManifest(long checkpointId) throws IOException {
        if (writeResultsOfCurrentCkpt.isEmpty()) {
            return EMPTY_MANIFEST_DATA;
        }

        WriteResult result = WriteResult.builder().addAll(writeResultsOfCurrentCkpt).build();
        DeltaManifests deltaManifests =
                FlinkManifestUtil.writeCompletedFiles(
                        result, () -> manifestOutputFileFactory.create(checkpointId), spec);

        return SimpleVersionedSerialization.writeVersionAndSerialize(
                DeltaManifestsSerializer.INSTANCE, deltaManifests);
    }
Write all the complete data files to a newly created manifest file and return the manifest's
avro serialized bytes.
inlong-sort/sort-flink/sort-flink-v1.15/sort-connectors/iceberg/src/main/java/org/apache/inlong/sort/iceberg/sink/IcebergFilesCommitter.java