docstr: Confirm rank normalized Split R-hat statistic is
  far from 1 for a small number of samples.
code: def test_rhat_bad(self):
      """Confirm rank normalized Split R-hat statistic is
      far from 1 for a small number of samples."""
      r_hat = rhat(
          np.vstack(
              [20 + np.random.randn(1, 100), np.random.randn(1, 100)]
          )
      )
      assert 1 / GOOD_RHAT > r_hat or GOOD_RHAT < r_hat
  
imports: import os
  import numpy
  import packaging
  import pandas
  import pytest
  import scipy
  from numpy.testing import assert_almost_equal
  from ...data import from_cmdstan, load_arviz_data
  from ...rcparams import rcParams
  from ...sel_utils import xarray_var_iter
  from ...stats import bfmi, ess, mcse, rhat
  from ...stats.diagnostics import _ess, _ess_quantile, _mc_error, _mcse_quantile, _multichain_statistics, _rhat, _rhat_rank, _split_chains, _z_scale, ks_summary
label_desc: Use image node_id 9 for calling the TestDiagnostics obj's underlying member method code with example usage: obj.test_rhat_bad() without return types