code: def test_var_names_warning():
      """Test confusing var_name handling"""
      data = from_dict(
          posterior={
              "~mu": np.random.randn(2, 10),
              "mu": -np.random.randn(
                  2, 10
              ),  # pylint: disable=invalid-unary-operand-type
              "theta": np.random.randn(2, 10, 8),
          }
      ).posterior
      var_names = expected = ["~mu"]
      with pytest.warns(UserWarning):
          assert _var_names(var_names, data) == expected
  
imports: from unittest.mock import Mock
  import numpy
  import pytest
  import scipy.stats
  from ...data import dict_to_dataset, from_dict, load_arviz_data
  from ...stats.density_utils import _circular_mean, _normalize_angle, _find_hdi_contours
  from ...utils import _stack, _subset_list, _var_names, expand_dims, flatten_inference_data_to_dict, one_de, two_de
  from ..helpers import TestRandomVariable
label_desc: Use image node_id 4 for calling a global function with example usage: test_var_names_warning() without return types