code: def __init__(self, parentfile, offset, length, name=None):
      self._file = parentfile
      self._offset = offset
      self._length = length
      self._end = offset + length
      self._pos = 0
  
      self.name = name
      self.closed = False
  
imports: import errno
  import os
  import sys
  from threading import Lock
  from shutil import copyfileobj
  from whoosh.compat import BytesIO, memoryview_
  from whoosh.filedb.structfile import BufferFile, StructFile
  from whoosh.filedb.filestore import FileStorage, StorageError
  from whoosh.system import emptybytes
  from whoosh.util import random_name
label_desc: Use image node_id 1 to create a new SubFile object from inherited base classes: object with example: obj = SubFile(parentfile, offset, length, name)