code: def maybe_download_ann_file(cfg: mmcv.Config) -> None:
      """
      mmdetection expects the annotation files to be available in the disk at a specific directory
      to initialize a dataset.  However, the annotation file is usually not available locally when a
      cloud backend is used. We will try to download the annotation file if it exists from the cloud
      if the backend is gcp or s3.
  
      Arguments:
          cfg: mmcv.Config with dataset specifications.
      """
      if "dataset" in cfg:
          dataset = cfg.dataset
      else:
          dataset = cfg
      ann_dir = "/".join(dataset.ann_file.split("/")[0:-1])
      os.makedirs(ann_dir, exist_ok=True)
      lock = filelock.FileLock(dataset.ann_file + ".lock")
  
      with lock:
          if not os.path.isfile(dataset.ann_file):
              try:
                  assert (
                      dataset.pipeline[0].type == "LoadImageFromFile"
                  ), "First step of dataset.pipeline is not LoadImageFromFile."
                  file_client_args = dataset.pipeline[
                      0
                  ].file_client_args
                  file_client = mmcv.FileClient(**file_client_args)
                  ann_bytes = file_client.get(dataset.ann_file)
                  logging.info(
                      f'Downloading annotation file using {file_client_args["backend"]} backend.'
                  )
                  with open(dataset.ann_file, "wb") as f:
                      f.write(ann_bytes)
              except Exception as e:
                  logging.error(
                      f"Could not download missing annotation file.  Encountered {e}."
                      f"Please make sure it is available at the following path {dataset.ann_file}."
                  )
  
imports: import functools
  import logging
  import math
  import os
  from typing import Any, Iterator, List, Tuple
  import filelock
  import mmcv
  import mmcv.parallel
  import mmdet.datasets
  import numpy
  import torch
  import torch.utils.data
  import determined.pytorch
label_desc: Use image node_id 1 for calling a global function with example usage: maybe_download_ann_file(cfg) without return types