code: def stack_or_none(
      tensors: Sequence[torch.Tensor], dim: int
  ) -> torch.Tensor:
      """
      Does exactly the same as :attr:`torch.stack` if the tensors can be concatenated
      without any memory operation. Otherwise returns None.
      """
      return _StackOrNone.apply(dim, *tensors)
  
file_path: xformers/xformers/ops/unbind.py
imports: from typing import List, Optional, Sequence, Tuple, Union
  import torch
  from .common import _get_storage_base
label_desc: Use image node_id 5 for calling a global function with example usage: stack_or_none(tensors, dim) and returns: _StackOrNone