code: def test_fit_a_linreg(self):
      model = StatsForecastAutoETS(season_length=12, model="ZZZ")
      model.fit(
          series=self.ts_pass_train,
          future_covariates=self.ts_trend_train,
      )
  
      # check if linear regression was fit
      assert model._linreg is not None
      assert model._linreg._fit_called
  
      # fit a linear regression
      linreg = LinearRegressionModel(lags_future_covariates=[0])
      linreg.fit(
          series=self.ts_pass_train,
          future_covariates=self.ts_trend_train,
      )
  
      # check if the linear regression was fit on the same data by checking if the coefficients are equal
      assert model._linreg.model.coef_ == linreg.model.coef_
  
file_path: darts/darts/tests/models/forecasting/test_sf_auto_ets.py
imports: import numpy
  import pandas
  from darts import TimeSeries
  from darts.datasets import AirPassengersDataset
  from darts.metrics import mae
  from darts.models import LinearRegressionModel, StatsForecastAutoETS
label_desc: Use image node_id 2 for calling the TestStatsForecastAutoETS obj's underlying member method code with example usage: obj.test_fit_a_linreg() without return types