code: def test_predict_regressor():
      """Test predict method of Regressor class."""
      df_train = pd.read_csv("data_for_tests/clean_train.csv")
      y_train = pd.read_csv(
          "data_for_tests/clean_target.csv", squeeze=True
      )
      regressor = Regressor()
      with pytest.raises(ValueError):
          regressor.predict(df_train)
      regressor.fit(df_train, y_train)
      with pytest.raises(ValueError):
          regressor.predict(None)
      assert len(regressor.predict(df_train)) > 0
  
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 7 for calling a global function with example usage: test_predict_regressor() without return types