code: def test_init_window_size_is_increased_when_differentiation(dif):
      """
      Test window_size is increased when including differentiation.
      """
      window_size = 5
  
      forecaster = ForecasterAutoregCustom(
          regressor=LinearRegression(),
          fun_predictors=create_predictors,
          window_size=window_size,
          differentiation=dif,
      )
  
      assert forecaster.window_size == window_size + dif
  
file_path: skforecast/skforecast/ForecasterAutoregCustom/tests/test_init.py
imports: import re
  import pytest
  import pandas
  import numpy
  from skforecast.ForecasterAutoregCustom import ForecasterAutoregCustom
  from skforecast.exceptions import IgnoredArgumentWarning
  from sklearn.linear_model import LinearRegression
  from sklearn.neighbors import KNeighborsRegressor
label_desc: Use image node_id 4 for calling a global function with example usage: test_init_window_size_is_increased_when_differentiation(dif) without return types