code: def test_mean(self):
      mn = self.descriptive.mean
      assert_allclose(mn, self.mean, rtol=1e-4)
  
imports: import numpy
  from scipy import stats
  import pandas
  from numpy.testing import assert_, assert_almost_equal, assert_allclose
  from statsmodels.stats.weightstats import DescrStatsW, CompareMeans, ttest_ind, ztest, zconfint
  from statsmodels.tools.testing import Holder
label_desc: Use image node_id 3 for calling the CheckExternalMixin obj's underlying member method code with example usage: obj.test_mean() without return types