code: def test_external_source_callback_torch_stream():
      for src_device in ["cpu", "gpu"]:
          for gen_device in ["cpu", "cuda"]:
              yield _test_external_source_callback_torch_stream, src_device, gen_device
  
file_path: DALI/dali/test/python/test_external_source_pytorch_dlpack.py
imports: import numpy
  import nvidia.dali.fn
  import nvidia.dali.ops
  import torch
  from nvidia.dali.backend_impl import *
  from nvidia.dali import Pipeline
  from torch.utils.dlpack import to_dlpack, from_dlpack
  from test_utils import check_output
label_desc: Use image node_id 6 for calling a global function with example usage: test_external_source_callback_torch_stream() without return types