code: def test_set_unknown():
      ds = Docstring(good)
      with pytest.raises(ValueError):
          ds._ds["Unknown"] = ["unknown"]
  
file_path: statsmodels/statsmodels/tools/tests/test_docstring.py
imports: import pytest
  from statsmodels.tools.docstring import Docstring, remove_parameters, Parameter
label_desc: Use image node_id 3 for calling a global function with example usage: test_set_unknown() without return types