code: def test_history(self):
      np.random.seed(3235)
      exog = np.random.normal(size=(300, 4))
      groups = np.kron(np.arange(100), [1, 1, 1])
      g_errors = np.kron(np.random.normal(size=100), [1, 1, 1])
      endog = exog.sum(1) + g_errors + np.random.normal(size=300)
      mod = MixedLM(endog, exog, groups)
      rslt = mod.fit(full_output=True)
      assert_equal(hasattr(rslt, "hist"), True)
  
imports: from statsmodels.compat.platform import PLATFORM_OSX
  import os
  import csv
  import warnings
  import numpy
  import pandas
  from scipy import sparse
  import pytest
  from statsmodels.regression.mixed_linear_model import MixedLM, MixedLMParams, _smw_solver, _smw_logdet
  from numpy.testing import assert_almost_equal, assert_equal, assert_allclose, assert_
  from statsmodels.base import _penalties
  import statsmodels.tools.numdiff
  from .results import lme_r_results
label_desc: Use image node_id 3 for calling the TestMixedLM obj's underlying member method code with example usage: obj.test_history() without return types