code: def test_missing_file():
      # The function is invoking a dummy workflow with a non-existent file.
      # So, an OSError will be raised.
  
      class TestMissingFile(Workflow):
          def run(self, filename, out_dir=""):
              """Dummy Workflow used to test if input file is absent.
  
              Parameters
              ----------
  
              filename : string
                  path of the first input file.
              out_dir: string, optional
                  folder path to save the results.
              """
              io = self.get_io_iterator()
  
      dummyflow = TestMissingFile()
      with TemporaryDirectory() as tempdir:
          npt.assert_raises(
              OSError, dummyflow.run, pjoin(tempdir, "dummy_file.txt")
          )
  
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 4 for calling a global function with example usage: test_missing_file() without return types