code: def test_initialize_lags_grid_when_lags_grid_is_None(
      lags, lags_grid_expected
  ):
      """
      Test initialize_lags_grid when lags_grid is None.
      """
      forecaster = ForecasterAutoreg(
          regressor=Ridge(random_state=123), lags=lags
      )
      lags_grid = None
      lags_grid, lags_label = initialize_lags_grid(
          forecaster, lags_grid
      )
  
      assert lags_label == "values"
      assert lags_grid.keys() == lags_grid_expected.keys()
      for v, v_expected in zip(
          lags_grid.values(), lags_grid_expected.values()
      ):
          assert v == v_expected
  
file_path: skforecast/skforecast/utils/tests/test_initialize_lags_grid.py
imports: import re
  import pytest
  import numpy
  import pandas
  from sklearn.linear_model import Ridge
  from skforecast.ForecasterAutoreg import ForecasterAutoreg
  from skforecast.ForecasterAutoregCustom import ForecasterAutoregCustom
  from skforecast.ForecasterAutoregMultiSeriesCustom import ForecasterAutoregMultiSeriesCustom
  from skforecast.utils import initialize_lags_grid
  from skforecast.exceptions import IgnoredArgumentWarning
label_desc: Use image node_id 5 for calling a global function with example usage: test_initialize_lags_grid_when_lags_grid_is_None(lags, lags_grid_expected) without return types