@Override
  public PlanNode clone() {
    return new FilterNode(
        getPlanNodeId(), outputExpressions, predicate, keepNull, scanOrder, fromWhere);
  }
This construction method is only used in inner of class `FilterNode`.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/planner/plan/node/process/FilterNode.java