code: def test_check_classes():
      for which_classes in [None, []]:
          which_classes = _check_classes(which_classes, 4)
          assert which_classes == [0, 1, 2, 3]
  
      for n_classes in range(3):
          which_classes = _check_classes(None, n_classes)
          assert which_classes == [0]
  
      which_classes = _check_classes([0, 2], 4)
      assert which_classes == [0, 2]
  
      with pytest.raises(
          ValueError, match="class index should be >= 0"
      ):
          _check_classes([-1, 0, 1], 3)
  
      with pytest.raises(
          ValueError, match="class index should be < n_classes"
      ):
          _check_classes([0, 3], 3)
  
imports: import pandas
  import numpy
  import pytest
  from pdpbox.utils import FeatureInfo, _to_rgba, _check_col, _check_dataset, _make_list, _check_model, _check_classes, _check_memory_limit, _check_frac_to_plot, _calc_n_jobs, _get_string, _expand_params_for_interact, _calc_preds, _check_cluster_params, _check_plot_engine, _check_pdp_interact_plot_type
label_desc: Use image node_id 5 for calling a global function with example usage: test_check_classes() without return types