code: def test_data_parallel_single_gpu():
      with pytest.warns(UserWarning, match="much slower"):
          module = DataParallel(torch.nn.Identity())
      data_list = [Data(x=torch.randn(x, 1)) for x in [2, 3, 10, 4]]
      batches = module.scatter(data_list, device_ids=[0])
      assert len(batches) == 1
  
imports: import pytest
  import torch
  from torch_geometric.data import Data
  from torch_geometric.nn import DataParallel
  from torch_geometric.testing import onlyCUDA
label_desc: Use image node_id 1 for calling a global function with example usage: test_data_parallel_single_gpu() without return types