code: def test_maxtasksperchild(shutdown_only):
      def f(args):
          return os.getpid()
  
      pool = Pool(5, maxtasksperchild=1)
      assert len(set(pool.map(f, range(20)))) == 20
      pool.terminate()
      pool.join()
  
imports: import os
  import sys
  import platform
  import pytest
  import tempfile
  import time
  import random
  from collections import defaultdict
  import queue
  import math
  import ray
  from ray._private.test_utils import SignalActor
  from ray.util.multiprocessing import Pool, TimeoutError, JoinableQueue
  from ray.util.joblib import register_ray
  from joblib import parallel_backend, Parallel, delayed
label_desc: Use image node_id 23 for calling a global function with example usage: test_maxtasksperchild(shutdown_only) and returns: os