code: def test_omp_threads_set(ray_start_cluster, monkeypatch):
      import os
  
      cluster = ray_start_cluster
      cluster.add_node(num_cpus=2)
      ray.init(address=cluster.address)
  
      @ray.remote
      def f():
          return os.environ.get("OMP_NUM_THREADS")
  
      @ray.remote
      class Actor:
          def f(self):
              return os.environ.get("OMP_NUM_THREADS")
  
      ###########################
      # Test basic tasks
      ###########################
      # Test override to num_cpus if OMP_NUM_THREADS not set
      assert ray.get(f.options(num_cpus=2).remote()) == "2"
  
      # Test override to default cpu number if OMP_NUM_THREADS not set
      assert ray.get(f.remote()) == "1"
  
      # Test set to 1 for fractional CPU
      assert ray.get(f.options(num_cpus=0.25).remote()) == "1"
  
      ###########################
      # Test not overriding env_variables
      ###########################
      from ray.runtime_env import RuntimeEnv
  
      assert (
          ray.get(
              f.options(
                  runtime_env=RuntimeEnv(
                      env_vars={"OMP_NUM_THREADS": "2"}
                  )
              ).remote()
          )
          == "2"
      )
      assert (
          ray.get(
              f.options(
                  num_cpus=1,
                  runtime_env=RuntimeEnv(
                      env_vars={"OMP_NUM_THREADS": "2"}
                  ),
              ).remote()
          )
          == "2"
      )
  
      ###########################
      # Test actor tasks
      ###########################
      # Test actor tasks set OMP_NUM_THREADS correctly in a similar way.
      assert ray.get(Actor.remote().f.remote()) == "1"
      assert (
          ray.get(Actor.options(num_cpus=2).remote().f.remote()) == "2"
      )
      assert (
          ray.get(Actor.options(num_cpus=0.25).remote().f.remote())
          == "1"
      )
  
      ###########################
      # Test setting and restoring of the environ after tasks run
      ###########################
      @ray.remote
      def g():
          return os.getpid(), os.environ.get("OMP_NUM_THREADS")
  
      # Set to 1
      pid1, omp_num_threads = ray.get(g.remote())
      assert omp_num_threads == "1"
      # Set to 2
      pid2, omp_num_threads = ray.get(g.options(num_cpus=2).remote())
      assert pid1 == pid2
      assert omp_num_threads == "2"
  
      ###########################
      # Test not setting the value with environ already set to 1 in env
      ###########################
      with monkeypatch.context() as m:
          m.setenv("OMP_NUM_THREADS", "1")
          cluster.add_node(num_cpus=4)
      assert ray.get(f.options(num_cpus=4).remote()) == "1"
  
imports: import logging
  import os
  import pickle
  import random
  import sys
  import time
  import pytest
  import ray
  import ray.cluster_utils
  from ray._private.test_utils import SignalActor, client_test_enabled, get_error_message, run_string_as_driver
label_desc: Use image node_id 8 for calling a global function with example usage: test_omp_threads_set(ray_start_cluster, monkeypatch) and returns: os, os,  os, os