code: def open_file(self, fname, mode, offset=None):
      if not os.path.exists(fname):
          raise RuntimeError("Dataset does not exist")
      try:
          self.fname = fname
          self.mode = mode
          self._fp = open(fname, mode)
          if offset is not None:
              self._fp.seek(offset, io.SEEK_SET)
          self.offset = self._fp.tell()
      except Exception as e:
          print(
              "Error {}: reading blocks in open_file {}!".format(
                  e, self.fname
              )
          )
          time.sleep(10)
          self.open_file(fname, mode, offset)
  
imports: import io
  import os
  import struct
  from typing import List, Optional, Set
  import torch
  import bisect
  import bmtrain
  import json
  from .serializer import Serializer, PickleSerializer
  import random
  import string
  import time
label_desc: Use image node_id 6 for calling the SafeFile obj's underlying member method code with example usage: obj.open_file(fname, mode, offset) without return types