code: def test_external_source_with_callback():
      """Test if using external_source with 'source' doesn't raise exceptions."""
      pipe = pipeline()
      pipe.build()
      pipe.run()
  
imports: import nvidia.dali.fn
  from nvidia.dali import pipeline_def, Pipeline
  import numpy
  from nose_utils import raises
label_desc: Use image node_id 3 for calling a global function with example usage: test_external_source_with_callback() without return types