code: def test_recursive_predict_output_when_regressor_is_LinearRegression_StandardScaler():
      """
      Test _recursive_predict output when using LinearRegression as regressor and
      StandardScaler.
      """
      series = pd.DataFrame(
          {
              "1": pd.Series(np.arange(start=0, stop=50)),
              "2": pd.Series(np.arange(start=50, stop=100)),
          }
      )
  
      forecaster = ForecasterAutoregMultiSeriesCustom(
          regressor=Ridge(random_state=123),
          fun_predictors=create_predictors,
          window_size=5,
      )
      forecaster.fit(series=series)
      level = "1"
      predictions_1 = forecaster._recursive_predict(
          steps=5,
          level=level,
          last_window=forecaster.last_window[level].to_numpy(),
          exog=None,
      )
      expected_1 = np.array(
          [
              47.07918986,
              47.49389001,
              47.79185048,
              47.94978724,
              47.93977217,
          ]
      )
  
      level = "2"
      predictions_2 = forecaster._recursive_predict(
          steps=5,
          level=level,
          last_window=forecaster.last_window[level].to_numpy(),
          exog=None,
      )
      expected_2 = np.array(
          [
              96.94237815,
              97.32979082,
              97.59502126,
              97.71369989,
              97.65659655,
          ]
      )
  
      assert predictions_1 == approx(expected_1)
      assert predictions_2 == approx(expected_2)
  
file_path: skforecast/skforecast/ForecasterAutoregMultiSeriesCustom/tests/test_recursive_predict.py
imports: from pytest import approx
  import numpy
  import pandas
  from sklearn.linear_model import Ridge
  from sklearn.linear_model import LinearRegression
  from skforecast.ForecasterAutoregMultiSeriesCustom import ForecasterAutoregMultiSeriesCustom
label_desc: Use image node_id 3 for calling a global function with example usage: test_recursive_predict_output_when_regressor_is_LinearRegression_StandardScaler() without return types