code: def make_folder_for_today(log_dir):
      
      now = datetime.datetime.now()
      sub_folders_list = ['{0:04d}'.format(now.year),
                          '{0:02d}'.format(now.month),
                          '{0:02d}'.format(now.day)]
      folder = log_dir
      for sf in sub_folders_list:
          folder = os.path.join(folder, sf)
          if not os.path.exists(folder):
              os.makedirs(folder)
      return folder
docs: Creates the folder log_dir/yyyy/mm/dd in log_dir if it doesn't exist
      and returns the full path of the folder.