code: def test_need_pos_label(self):
      expected_msg = "If pos_label is not specified, values must be from {0, 1} or {-1, 1}"
      with pytest.raises(ValueError) as e0:
          _get_labels_for_confusion_matrix([0, 2], None)
      assert str(e0.value) == expected_msg
      with pytest.raises(ValueError) as e1:
          _get_labels_for_confusion_matrix([-1, 0], None)
      assert str(e1.value) == expected_msg
  
imports: import numpy
  import pytest
  import sklearn.metrics
  import fairlearn.metrics
  from fairlearn.metrics._base_metrics import _get_labels_for_confusion_matrix
label_desc: Use image node_id 8 for calling the TestGetLabelsForConfusionMatrix obj's underlying member method code with example usage: obj.test_need_pos_label() without return types