code: def test_unique_labels():
      # Empty iterable
      with pytest.raises(ValueError):
          unique_labels()
  
      # Multiclass problem
      assert_array_equal(unique_labels(range(10)), np.arange(10))
      assert_array_equal(unique_labels(np.arange(10)), np.arange(10))
      assert_array_equal(unique_labels([4, 0, 2]), np.array([0, 2, 4]))
  
      # Multilabel indicator
      assert_array_equal(
          unique_labels(np.array([[0, 0, 1], [1, 0, 1], [0, 0, 0]])),
          np.arange(3),
      )
  
      assert_array_equal(
          unique_labels(np.array([[0, 0, 1], [0, 0, 0]])), np.arange(3)
      )
  
      # Several arrays passed
      assert_array_equal(
          unique_labels([4, 0, 2], range(5)), np.arange(5)
      )
      assert_array_equal(
          unique_labels((0, 1, 2), (0,), (2, 1)), np.arange(3)
      )
  
      # Border line case with binary indicator matrix
      with pytest.raises(ValueError):
          unique_labels([4, 0, 2], np.ones((5, 5)))
      with pytest.raises(ValueError):
          unique_labels(np.ones((5, 4)), np.ones((5, 5)))
  
      assert_array_equal(
          unique_labels(np.ones((4, 5)), np.ones((5, 5))), np.arange(5)
      )
  
imports: from itertools import product
  import numpy
  import pytest
  from scipy.sparse import issparse
  from sklearn import config_context, datasets
  from sklearn.model_selection import ShuffleSplit
  from sklearn.svm import SVC
  from sklearn.utils._array_api import yield_namespace_device_dtype_combinations
  from sklearn.utils._testing import _array_api_for_tests, assert_allclose, assert_array_almost_equal, assert_array_equal
  from sklearn.utils.estimator_checks import _NotAnArray
  from sklearn.utils.fixes import COO_CONTAINERS, CSC_CONTAINERS, CSR_CONTAINERS, DOK_CONTAINERS, LIL_CONTAINERS
  from sklearn.utils.metaestimators import _safe_split
  from sklearn.utils.multiclass import _ovr_decision_function, check_classification_targets, class_distribution, is_multilabel, type_of_target, unique_labels
label_desc: Use image node_id 2 for calling a global function with example usage: test_unique_labels() without return types