code: def main():
      threads = []
      for i in range(20):
          threads.append(threading.Thread(target=t))
      for thread in threads:
          thread.start()
      for thread in threads:
          thread.join()
  
imports: import multiprocessing
  import os
  import threading
  import traceback
label_desc: Use image node_id 2 for calling a global function with example usage: main() without return types