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)
  
      if os.path.exists(local_chunkpath):
          return
  
      if self._downloader is None:
          raise RuntimeError("The downloader should be defined.")
  
      self._downloader.download_chunk_from_index(chunk_index)
  
imports: import json
  import os
  from typing import Any, Dict, List, Optional, Tuple
  from lightning.data.streaming.constants import _INDEX_FILENAME, _TORCH_GREATER_EQUAL_2_1_0
  from lightning.data.streaming.downloader import get_downloader_cls
  from lightning.data.streaming.item_loader import BaseItemLoader, PyTreeLoader, TokensLoader
  from lightning.data.streaming.sampler import ChunkedIndex
  from lightning.data.streaming.serializers import Serializer
label_desc: Use image node_id 2 for calling the ChunksConfig obj's underlying member method code with example usage: obj.download_chunk_from_index(chunk_index) without return types