code: def test_nonstring_var_names():
      """Check that non-string variables are preserved"""
      mu = TestRandomVariable("mu")
      samples = np.random.randn(10)
      data = dict_to_dataset({mu: samples})
      assert _var_names([mu], data) == [mu]
  
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 8 for calling a global function with example usage: test_nonstring_var_names() without return types