@Override
  public void close() throws IOException {
    if (loader != null) {
      loader.close();
    }
  }
Used for MergeOnRead, only for the bounded reading and return append stream.
amoro-format-mixed/amoro-mixed-flink/amoro-mixed-flink-common/src/main/java/org/apache/amoro/flink/read/hybrid/enumerator/MergeOnReadPlannerImpl.java