@Override
  public MixedFormatSourceEnumState snapshotState(long checkpointId) throws Exception {
    long[] shuffleSplitRelation = null;
    if (splitAssigner instanceof ShuffleSplitAssigner) {
      shuffleSplitRelation = ((ShuffleSplitAssigner) splitAssigner).serializePartitionIndex();
    }
    return new MixedFormatSourceEnumState(
        splitAssigner.state(), enumeratorPosition.get(), shuffleSplitRelation, temporalJoinSplits);
  }
Check whether all first splits have been finished or not. After all finished, enumerator will
send a {@link InitializationFinishedEvent} to notify all {@link MixedFormatSourceReader}.

@param finishedSplitIds
amoro-format-mixed/amoro-mixed-flink/amoro-mixed-flink-common/src/main/java/org/apache/amoro/flink/read/hybrid/enumerator/MixedFormatSourceEnumerator.java