code: def test_additive_detrending_series(y_series):
      """Tests we get the expected result when setting `model=additive`."""
      # Load test dataset
      y = y_series
  
      # Get the trend
      forecaster = PolynomialTrendForecaster(
          degree=1, with_intercept=True
      )
      trend = forecaster.fit_predict(y, fh=y.index)
  
      # De-trend the time series
      detrender = Detrender(forecaster, model="additive")
      y_transformed = detrender.fit_transform(y)
  
      # Compute the expected de-trended time series
      expected = y - trend
  
      pd.testing.assert_series_equal(y_transformed, expected)
  
file_path: sktime/sktime/transformations/series/detrend/tests/test_detrend.py
imports: import numpy
  import pandas
  import pytest
  from sktime.datasets import load_airline
  from sktime.forecasting.trend import PolynomialTrendForecaster
  from sktime.forecasting.trend.tests.test_trend import get_expected_polynomial_coefs
  from sktime.transformations.series.detrend import Detrender
label_desc: Use image node_id 6 for calling a global function with example usage: test_additive_detrending_series(y_series) without return types