code: def test_MICE1_regularized(self):
      df = gendat()
      imp = mice.MICEData(df, perturbation_method="boot")
      imp.set_imputer("x1", "x2 + y", fit_kwds={"alpha": 1, "L1_wt": 0})
      imp.update_all()
  
imports: import numpy
  import pandas
  import pytest
  from statsmodels.imputation import mice
  import statsmodels.api
  from numpy.testing import assert_equal, assert_allclose
  import warnings
label_desc: Use image node_id 3 for calling the TestMICE obj's underlying member method code with example usage: obj.test_MICE1_regularized() without return types