code: def _apply(self, fn: Callable) -> None:
      self._device = fn(torch.zeros(1)).device
      return self
  
imports: from typing import Optional, Callable
  import torch
  from torch import Tensor
  from torch.cuda import Stream
  from dig_ext.sync import synchronize, read_async, write_async
label_desc: Use image node_id 2 for calling the AsyncIOPool obj's underlying member method code with example usage: obj._apply(fn) and returns: self