code: def _cat(tensors: List[Tensor], dim: int = 0) -> Tensor:
      """
      Efficient version of torch.cat that avoids a copy if there is only a single element in a list
      """
      # TODO add back the assert
      # assert isinstance(tensors, (list, tuple))
      if len(tensors) == 1:
          return tensors[0]
      return torch.cat(tensors, dim)
  
file_path: vision/torchvision/ops/_utils.py
imports: from typing import List, Optional, Tuple, Union
  import torch
  from torch import nn, Tensor
label_desc: Use image node_id 1 for calling a global function with example usage: _cat(tensors, dim) and returns: torch, tensors