code: def test_split_chain_dims(self, chains, draws):
      if chains is None:
          data = np.random.randn(draws)
      else:
          data = np.random.randn(chains, draws)
      split_data = _split_chains(data)
      if chains is None:
          chains = 1
      assert split_data.shape == (chains * 2, draws // 2)
  
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 30 for calling the TestDiagnostics obj's underlying member method code with example usage: obj.test_split_chain_dims(chains, draws) without return types