code: def test_sem(self):
      # Use default vardef in SAS to match; only makes sense if
      # weights sum to n.
      if not hasattr(self, "sem"):
          return
      sem = self.descriptive.std_mean
      assert_allclose(sem, self.sem, 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 7 for calling the CheckExternalMixin obj's underlying member method code with example usage: obj.test_sem() without return types