docstr: Write the chunks index to a JSON file.
docstr_tok: ["Write","the","chunks","index","to","a","JSON","file","."]
code: def write_chunks_index(self) -> str:
      """Write the chunks index to a JSON file."""
      filepath = os.path.join(
          self._cache_dir, f"{self.rank}.{_INDEX_FILENAME}"
      )
      config = self.get_config()
      with open(filepath, "w") as out:
          json.dump(
              {"chunks": self._chunks_info, "config": config},
              out,
              sort_keys=True,
          )
      return filepath
  
imports: import json
  import os
  import warnings
  from dataclasses import dataclass
  from time import sleep
  from typing import Any, Dict, List, Optional, Tuple, Union
  import numpy
  import torch
  from lightning.data.streaming.compression import _COMPRESSORS, Compressor
  from lightning.data.streaming.constants import _INDEX_FILENAME, _TORCH_GREATER_EQUAL_2_1_0
  from lightning.data.streaming.serializers import Serializer, _get_serializers
  from lightning.data.utilities.env import _DistributedEnv, _WorkerEnv
  from lightning.data.utilities.format import _convert_bytes_to_int, _human_readable_bytes
label_desc: Use image node_id 14 for calling the BinaryWriter obj's underlying member method code with example usage: obj.write_chunks_index() and returns: filepath