@Override
  public Collection<MixedFormatSplitState> state() {
    List<MixedFormatSplitState> mixedFormatSplitStates = new ArrayList<>();
    subtaskSplitMap.forEach(
        (key, value) ->
            mixedFormatSplitStates.addAll(
                value.stream().map(MixedFormatSplitState::new).collect(Collectors.toList())));

    return mixedFormatSplitStates;
  }
Key is subtaskId, Value is the queue of unAssigned mixed-format splits.
amoro-format-mixed/amoro-mixed-flink/amoro-mixed-flink-common/src/main/java/org/apache/amoro/flink/read/hybrid/assigner/ShuffleSplitAssigner.java