code: def test_init_window_size_is_increased_when_differentiation(dif):
      """
      Test window_size is increased when including differentiation.
      """
      forecaster = ForecasterAutoreg(
          regressor=LinearRegression(), lags=5, differentiation=dif
      )
  
      assert forecaster.window_size == len(forecaster.lags) + dif
  
file_path: skforecast/skforecast/ForecasterAutoreg/tests/test_init.py
imports: import re
  import pytest
  import numpy
  import pandas
  from sklearn.linear_model import LinearRegression
  from skforecast.ForecasterAutoreg import ForecasterAutoreg
label_desc: Use image node_id 2 for calling a global function with example usage: test_init_window_size_is_increased_when_differentiation(dif) without return types