code: def test_fit_stacking_regressor():
      """Test fit method of StackingRegressor 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
      )
      stacking_regressor = StackingRegressor(verbose=True)
      stacking_regressor.fit(df_train, y_train)
      assert stacking_regressor._StackingRegressor__fitOK
  
file_path: MLBox/tests/test_stacking_regressor.py
imports: import pytest
  import pandas
  import numpy
  from sklearn.linear_model import LinearRegression
  from mlbox.model.regression.stacking_regressor import StackingRegressor
label_desc: Use image node_id 6 for calling a global function with example usage: test_fit_stacking_regressor() without return types