code: def _rhat_z_scale(ary):
      ary = np.asarray(ary)
      if _not_valid(ary, shape_kwargs=dict(min_draws=4, min_chains=2)):
          return np.nan
      return _rhat(_z_scale(_split_chains(ary)))
  
imports: import warnings
  from collections.abc import Sequence
  import numpy
  import packaging
  import pandas
  import scipy
  from scipy import stats
  from ..data import convert_to_dataset
  from ..utils import Numba, _numba_var, _stack, _var_names
  from .density_utils import histogram
  from .stats_utils import _circular_standard_deviation, _sqrt
  from .stats_utils import autocov
  from .stats_utils import not_valid
  from .stats_utils import quantile
  from .stats_utils import stats_variance_2d
  from .stats_utils import wrap_xarray_ufunc
label_desc: Use image node_id 14 for calling a global function with example usage: _rhat_z_scale(ary) and returns: _rhat, np