code: def test_set_regressor():
      """Test set method of Regressor class."""
      regressor = Regressor()
      with pytest.raises(ValueError):
          regressor._Regressor__set_regressor("wrong_strategy")
  
file_path: MLBox/tests/test_regressor.py
imports: import pytest
  import pandas
  import numpy
  from mlbox.model.regression.regressor import Regressor
  from lightgbm import LGBMRegressor
label_desc: Use image node_id 4 for calling a global function with example usage: test_set_regressor() without return types