code: def identity_fn(x: Union[torch.Tensor, list]) -> torch.Tensor:
      if isinstance(x, list):
          return torch.from_numpy(np.array(x))
      else:
          return x
  
file_path: alibi-detect/alibi_detect/cd/keops/tests/test_learned_kernel_keops.py
imports: from itertools import product
  import numpy
  import pytest
  import torch
  import torch.nn
  from typing import Callable, Optional, Union
  from alibi_detect.utils.frameworks import has_keops
  from alibi_detect.utils.pytorch import GaussianRBF
  from alibi_detect.utils.pytorch import mmd2_from_kernel_matrix
label_desc: Use image node_id 1 for calling a global function with example usage: identity_fn(x) and returns: torch, x