code: def fetch_and_preprocess(self, conn):
      begin_time = time.time()
      cur = conn.cursor()
      # Assuming you want to get the latest 100 rows
      columns_str = ", ".join(self.columns)
      # Select rows greater than last_id
      cur.execute(
          f"SELECT id, {columns_str} FROM {self.table} "
          f"WHERE id > {self.last_id} ORDER BY id ASC LIMIT {self.batch_size}"
      )
      rows = cur.fetchall()
  
      if rows:
          # Update last_id with max id of fetched rows
          self.last_id = max(
              row[0] for row in rows
          )  # assuming 'id' is at index 0
      else:
          # If no more new rows, reset last_id to start over scan and return 'end_position'
          self.last_id = -1
          return "end_position", time.time() - begin_time
  
      batch = self.pre_processing(rows)
      return batch, time.time() - begin_time
  
file_path: singa/examples/model_selection/TRAILS-Database-Native-Model-Selection/internal/cache-service/cache_service.py
imports: import time
  import threading
  import queue
  import psycopg2
  from typing import Any, List, Dict, Tuple
  from sanic import Sanic
  from sanic.response import json
  import calendar
  import os
  import logging
label_desc: Use image node_id 5 for calling the CacheService obj's underlying member method code with example usage: obj.fetch_and_preprocess(conn) and returns: batch,  unknown, str,  unknown