code: def set_cv2_num_threads(num_workers):
      # Limit cv2 threads if too many subprocesses are spawned.
      # This should reduce resource allocation and thus boost performance.
      nranks = paddle.distributed.ParallelEnv().nranks
      if nranks >= 8 and num_workers >= 8:
          logger.warning(
              "The number of threads used by OpenCV is "
              "set to 1 to improve performance."
          )
          cv2.setNumThreads(1)
  
imports: import os
  import contextlib
  import tempfile
  import random
  from urllib.parse import urlparse, unquote
  import yaml
  import numpy
  import paddle
  import cv2
  from paddleseg.utils import logger, seg_env, get_sys_env
  from paddleseg.utils.download import download_file_and_uncompress
label_desc: Use image node_id 6 for calling a global function with example usage: set_cv2_num_threads(num_workers) without return types