code: def finalize(self, index_file):
      self._data_file.close()
  
      with MMapIndexedDataset.Index.writer(
          index_file, self._dtype
      ) as index:
          index.write(self._sizes, self._doc_idx)
  
imports: import os
  import shutil
  import struct
  from functools import lru_cache
  from itertools import accumulate
  import numpy
  import torch
label_desc: Use image node_id 5 for calling the MMapIndexedDatasetBuilder obj's underlying member method code with example usage: obj.finalize(index_file) without return types