code: def test_volatility_shift_ad():
      model = VolatilityShiftAD(window=6)
      with pytest.raises(RuntimeError):
          model.fit(s)
  
      model = PersistAD(window=5)
      model.fit(s)
  
file_path: adtk/tests/test_few_shot_fit.py
imports: import numpy
  import pandas
  import pytest
  from adtk.detector import AutoregressionAD, LevelShiftAD, PersistAD, VolatilityShiftAD
label_desc: Use image node_id 3 for calling a global function with example usage: test_volatility_shift_ad() without return types