code: def purge_old_files(date_time, directory_path, custom_prefix="backup"):
      
      for file_name in listdir(directory_path):
          try:
              file_date_time = get_backup_file_time_tag(file_name, custom_prefix=custom_prefix)
          except ValueError as e:
              if "does not match format" in e.message:
                  print("WARNING. file(s) in %s do not match naming convention."
                        % (directory_path))
                  continue
              raise e
          if file_date_time < date_time:
              remove(directory_path + file_name)
docs: Takes a datetime object and a directory path, runs through files in the
          directory and deletes those tagged with a date from before the provided
          datetime.
          If your backups have a custom_prefix that is not the default ("backup"),
          provide it with the "custom_prefix" kwarg.