code: def _write_init(self):
      # keep last 8 bytes to record actual memory size
      self.shm = shm = SharedMemory(
          name=self._object_id, create=True, size=self._size + 8
      )
      self._write_actual_size()
      self._buffer = self._mv = shm.buf
  
imports: import asyncio
  import os
  import random
  import struct
  import sys
  from string import ascii_letters, digits
  from typing import Any, Dict, List, Tuple, Optional
  from dataclasses import dataclass
  from ..serialization import AioSerializer, AioDeserializer
  from ..utils import implements, dataslots
  from .base import StorageBackend, StorageLevel, ObjectInfo, register_storage_backend
  from .core import BufferWrappedFileObject, StorageFileObject
label_desc: Use image node_id 3 for calling the SharedMemoryFileObject obj's underlying member method code with example usage: obj._write_init() without return types