code: def test_run():
      wf = Workflow()
      npt.assert_raises(Exception, wf.run, None)
  
file_path: dipy/dipy/workflows/tests/test_workflow.py
imports: import os
  import time
  from os.path import join
  from tempfile import TemporaryDirectory
  import numpy.testing
  from dipy.data import get_fnames
  from dipy.workflows.segment import MedianOtsuFlow
  from dipy.workflows.workflow import Workflow
label_desc: Use image node_id 3 for calling a global function with example usage: test_run() without return types