class_docstr: This class is a data structure to keep the content in the index.json file for sharded checkpoint.
  
  Example:
      >>> index = CheckpointIndexFile.from_file('model.index.json')
      >>> index.append_metadata('model_type', 'bert')
      >>> index.append_weight_map('bert.embeddings.word_embeddings.weight', 'model_0001-of-0002.bin')
      >>> index.export('new_index.json')
class_docstr_tok: ["This","class","is","a","data","structure","to","keep","the","content","in","the","index.json","file","for","sharded","checkpoint",".","Example",":",">",">",">","index","=","CheckpointIndexFile.from_file","(","'model.index.json","'",")",">",">",">","index.append_metadata","(","'model_type","'",",","'bert","'",")",">",">",">","index.append_weight_map","(","'bert.embeddings.word_embeddings.weight","'",",","'model_0001-of-0002.bin","'",")",">",">",">","index.export","(","'new_index.json","'",")"]
docstr: Write index file.
docstr_tok: ["Write","index","file","."]
code: def write_index_file(self, save_index_file):
      """
      Write index file.
      """
      save_index_file = os.path.join(self.root_path, save_index_file)
      index = {"metadata": self.metadata, "weight_map": self.weight_map}
      with open(save_index_file, "w", encoding="utf-8") as f:
          content = json.dumps(index, indent=2) + "\n"
          f.write(content)
  
file_path: ColossalAI/colossalai/checkpoint_io/index_file.py
imports: import json
  import os
  from collections import OrderedDict
  from pathlib import Path
  from typing import Any, Dict, List, Union
  from .utils import is_dtensor_checkpoint
label_desc: Use image node_id 13 for calling the CheckpointIndexFile obj's underlying member method code with example usage: obj.write_index_file(save_index_file) without return types