code: def test_confusion_matrix_add(self):
      a = _classification._ConfusionMatrix(tp=4, tn=4, fp=2, fn=4)
      b = _classification._ConfusionMatrix(tp=1, tn=6, fp=9, fn=2)
      expected = _classification._ConfusionMatrix(
          tp=5, tn=10, fp=11, fn=6
      )
      self.assertEqual(a + b, expected)
  
imports: from absl.testing import absltest
  from absl.testing import parameterized
  import numpy
  from tensorflow_model_analysis.experimental.metrics.aggregates import _classification
label_desc: Use image node_id 10 for calling the ClassificationTest obj's underlying member method code with example usage: obj.test_confusion_matrix_add() without return types