@Override
  protected void serialize(DataOutputStream stream) throws IOException {
    ReadWriteIOUtils.write(startTime, stream);
    ReadWriteIOUtils.write(endTime, stream);
    interval.serialize(stream);
    slidingStep.serialize(stream);
  }
Only used for representing GROUP BY TIME filter.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/expression/other/GroupByTimeExpression.java