code: def _cuda_buffer(self, idx: int) -> Tensor:
      if self._cuda_buffers[idx] is None:
          assert str(self._device)[:4] == "cuda"
          self._cuda_buffers[idx] = torch.empty(
              self.buffer_size, self.embedding_dim, device=self._device
          )
      return self._cuda_buffers[idx]
  
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 6 for calling the AsyncIOPool obj's underlying member method code with example usage: obj._cuda_buffer(idx) and returns: self