class_docstr: Object class to write the index (.idx) file
  
  Args:
      idx_path (str): The path to the index file
  
      dtype (Type[numpy.number]): The dtype of the index file
class_docstr_tok: ["Object","class","to","write","the","index","(",".idx",")","file","Args",":","idx_path","(","str",")",":","The","path","to","the","index","file","dtype","(","Type","[","numpy.number","]",")",":","The","dtype","of","the","index","file"]
docstr: Enter the context introduced by the 'with' keyword
  
  Returns:
      _IndexWriter: The instance
docstr_tok: ["Enter","the","context","introduced","by","the","'with","'","keyword","Returns",":","_IndexWriter",":","The","instance"]
code: def __enter__(self) -> "_IndexWriter":
      """Enter the context introduced by the 'with' keyword
  
      Returns:
          _IndexWriter: The instance
      """
      self.idx_writer = open(self.idx_path, "wb")
      # fixed, vestigial practice
      self.idx_writer.write(_INDEX_HEADER)
      # fixed, vestigial practice
      self.idx_writer.write(struct.pack("<Q", 1))
      # the numeric code for the dtype
      self.idx_writer.write(
          struct.pack("<B", DType.code_from_dtype(self.dtype))
      )
      return self
  
imports: import logging
  import os
  import shutil
  import struct
  import time
  from enum import Enum
  from functools import lru_cache
  from itertools import accumulate
  from types import TracebackType
  from typing import List, Optional, Tuple, Type, Union
  import numpy
  import torch
  from megatron.core.datasets.utils import log_single_rank
label_desc: Use image node_id 2 for calling the _IndexWriter obj's underlying member method code with example usage: obj.__enter__() and returns: self