code: def _test_file_properties(device):
      root_path = os.path.join(
          test_data_root, "db", "single", "png", "0"
      )
      files = [
          os.path.join(root_path, i) for i in os.listdir(root_path)
      ]
      p = file_properties(
          files, device, batch_size=8, num_threads=4, device_id=0
      )
      p.build()
      output = p.run()
      for out in output:
          out = out if device == "cpu" else out.as_cpu()
          for source_info, ref in zip(out, files):
              assert _uint8_tensor_to_string(source_info) == ref
  
imports: from nvidia.dali import pipeline_def
  import os
  import numpy
  from nvidia.dali import fn
  from test_utils import get_dali_extra_path
  from nose_utils import raises
  import tempfile
label_desc: Use image node_id 3 for calling a global function with example usage: _test_file_properties(device) without return types