code: def test_empty_parameter(self):
      model_code = """
              parameters {
                  real y;
                  vector[3] x;
                  vector[0] a;
                  vector[2] z;
              }
              model {
                  y ~ normal(0,1);
              }
          """
      if pystan_version() == 2:
          from pystan import StanModel  # pylint: disable=import-error
  
          model = StanModel(model_code=model_code)
          fit = model.sampling(
              iter=500, chains=2, check_hmc_diagnostics=False
          )
      else:
          import stan  # pylint: disable=import-error
  
          model = stan.build(model_code)
          fit = model.sample(num_samples=500, num_chains=2)
  
      posterior = from_pystan(posterior=fit)
      test_dict = {
          "posterior": ["y", "x", "z", "~a"],
          "sample_stats": ["diverging"],
      }
      fails = check_multiple_attrs(test_dict, posterior)
      assert not fails
  
imports: import importlib
  from collections import OrderedDict
  import numpy
  import pytest
  from ...None import from_pystan
  from ...data.io_pystan import get_draws, get_draws_stan3
  from ..helpers import chains, check_multiple_attrs, draws, eight_schools_params, importorskip, load_cached_models, pystan_version, running_on_ci
label_desc: Use image node_id 10 for calling the TestDataPyStan obj's underlying member method code with example usage: obj.test_empty_parameter() without return types