code: def test_blockdiagonal(self):
      cov, nobs = self.cov, self.nobs
      # from Stata 14
      p_chi2 = 0.1721758850671037
      # df = 2
      chi2 = 3.518477474111563
  
      # cov_blocks = cov[:2, :2], cov[-1:, -1:]
      # stat, pv = smmv.test_cov_blockdiagonal(cov, nobs, cov_blocks)
      block_len = [2, 1]
      stat, pv = smmv.test_cov_blockdiagonal(cov, nobs, block_len)
      assert_allclose(stat, chi2, rtol=1e-7)
      assert_allclose(pv, p_chi2, rtol=1e-6)
  
file_path: statsmodels/statsmodels/stats/tests/test_multivariate.py
imports: import numpy
  from numpy.testing import assert_allclose, assert_equal
  from statsmodels.stats import weightstats
  import statsmodels.stats.multivariate
  from statsmodels.stats.multivariate import confint_mvmean_fromstats
  from statsmodels.tools.testing import Holder
label_desc: Use image node_id 4 for calling the TestCovStructure obj's underlying member method code with example usage: obj.test_blockdiagonal() without return types