code: def test_spin_up_down_threads(handler):
      assert len(handler.handle.thread_groups["preprocess"]) == 1
      assert len(handler.handle.thread_groups["inference"]) == 2
      assert len(handler.handle.thread_groups["postprocess"]) == 3
  
      new_parallelism = {
          "preprocess": 2,
          "inference": 3,
          "postprocess": 4,
      }
  
      handler.handle.parallelism = new_parallelism
  
      assert len(handler.handle.thread_groups["preprocess"]) == 2
      assert len(handler.handle.thread_groups["inference"]) == 3
      assert len(handler.handle.thread_groups["postprocess"]) == 4
  
      new_parallelism = {
          "preprocess": 1,
          "inference": 2,
          "postprocess": 3,
      }
  
      handler.handle.parallelism = new_parallelism
  
      assert len(handler.handle.thread_groups["preprocess"]) == 1
      assert len(handler.handle.thread_groups["inference"]) == 2
      assert len(handler.handle.thread_groups["postprocess"]) == 3
  
imports: import json
  import math
  import random
  import sys
  from pathlib import Path
  import pytest
  from torchvision.models.resnet import ResNet18_Weights
  from ts.handler_utils.micro_batching import MicroBatching
  from ts.torch_handler.image_classifier import ImageClassifier
  from ts.torch_handler.unit_tests.test_utils.mock_context import MockContext
  from ts.torch_handler.unit_tests.test_utils.model_dir import copy_files, download_model
label_desc: Use image node_id 13 for calling a global function with example usage: test_spin_up_down_threads(handler) without return types