code: def mark_done(path, version_string=None):
      """
      Mark this path as prebuilt.
  
      Marks the path as done by adding a '.built' file with the current timestamp
      plus a version description string if specified.
  
      :param str path:
          The file path to mark as built.
  
      :param str version_string:
          The version of this dataset.
      """
      with PathManager.open(os.path.join(path, ".built"), "w") as write:
          write.write(str(datetime.datetime.today()))
          if version_string:
              write.write("\n" + version_string)
  
imports: import importlib
  import json
  import time
  import datetime
  import os
  import requests
  import shutil
  import hashlib
  import tqdm
  import gzip
  import math
  import contextlib
  import parlai.utils.logging
  from parlai.utils.io import PathManager
label_desc: Use image node_id 2 for calling a global function with example usage: mark_done(path, version_string) without return types