code: def test_fit_em(self, **kwargs):
      # Test EM fitting (smoke test)
      res_em = self.model._fit_em(**kwargs)
      assert_allclose(
          res_em.llf,
          self.true["llf_fit_em"],
          atol=self.atol,
          rtol=self.rtol,
      )
  
imports: import os
  import warnings
  import numpy
  from numpy.testing import assert_allclose, assert_raises
  import pandas
  import pytest
  from statsmodels.tsa.regime_switching import markov_switching, markov_regression
label_desc: Use image node_id 5 for calling the MarkovRegression obj's underlying member method code with example usage: obj.test_fit_em() without return types