code: def merge_file_(self, another_file):
      index = IndexedDataset(another_file)
      assert index.dtype == self.dtype
  
      begin = self.data_offsets[-1]
      for offset in index.data_offsets[1:]:
          self.data_offsets.append(begin + offset)
      self.sizes.extend(index.sizes)
      begin = self.dim_offsets[-1]
      for dim_offset in index.dim_offsets[1:]:
          self.dim_offsets.append(begin + dim_offset)
  
      with open(data_file_path(another_file), "rb") as f:
          while True:
              data = f.read(1024)
              if data:
                  self.out_file.write(data)
              else:
                  break
  
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 4 for calling the IndexedDatasetBuilder obj's underlying member method code with example usage: obj.merge_file_(another_file) without return types