code: def test_none_or_dtype():
      # test None
      for typ in [int, float, str, tuple, list]:
          dec = none_or_dtype(typ)
          npt.assert_equal(dec("None"), "None")
          npt.assert_equal(dec("none"), "None")
  
      dec = none_or_dtype(int)
      npt.assert_raises(ValueError, dec, "my value")
      npt.assert_equal(dec(4), 4)
  
      dec = none_or_dtype(str)
      npt.assert_equal(dec(4), "4")
      npt.assert_equal(dec("my value"), "my value")
      npt.assert_equal(dec([4]), "[4]")
  
      dec = none_or_dtype(float)
      npt.assert_raises(ValueError, dec, "my value")
      for val in [
          (4,),
          [
              4,
          ],
      ]:
          npt.assert_raises(TypeError, dec, val)
      npt.assert_equal(dec(True), 1.0)
      npt.assert_equal(dec(4), 4.0)
      npt.assert_equal(dec(4.0), 4.0)
  
      dec = none_or_dtype(bool)
      dec = none_or_dtype(tuple)
  
file_path: dipy/dipy/workflows/tests/test_iap.py
imports: import sys
  from os.path import join
  from tempfile import TemporaryDirectory
  import numpy.testing
  from dipy.workflows.base import IntrospectiveArgumentParser, none_or_dtype
  from dipy.workflows.flow_runner import run_flow
  from dipy.workflows.tests.workflow_tests_utils import DummyFlow, DummyCombinedWorkflow, DummyWorkflow1, DummyWorkflowOptionalStr, DummyVariableTypeWorkflow, DummyVariableTypeErrorWorkflow
label_desc: Use image node_id 1 for calling a global function with example usage: test_none_or_dtype() without return types