@Override
  protected void serializeAttributes(ByteBuffer byteBuffer) {
    PlanNodeType.FILTER.serialize(byteBuffer);
    ReadWriteIOUtils.write(outputExpressions.length, byteBuffer);
    for (Expression expression : outputExpressions) {
      Expression.serialize(expression, byteBuffer);
    }
    Expression.serialize(predicate, byteBuffer);
    ReadWriteIOUtils.write(keepNull, byteBuffer);
    ReadWriteIOUtils.write(scanOrder.ordinal(), byteBuffer);
  }
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