code: def download_chunk_from_index(self, chunk_index: int) -> None:
      chunk_filename = self._chunks[chunk_index]["filename"]
      local_chunkpath = os.path.join(self._cache_dir, chunk_filename)
      remote_chunkpath = os.path.join(self._remote_dir, chunk_filename)
      self.download_file(remote_chunkpath, local_chunkpath)
  
file_path: pytorch-lightning/src/lightning/data/streaming/downloader.py
imports: import os
  import shutil
  from abc import ABC
  from typing import Any, Dict, List
  from urllib import parse
  from lightning.data.streaming.client import S3Client
label_desc: Use image node_id 2 for calling the Downloader obj's underlying member method code with example usage: obj.download_chunk_from_index(chunk_index) without return types