code: def test_values_at_duplicate_indices_are_summed(self):
      test_series = pd.DataFrame(
          [1.0, 2.0, 3.0, 4.0, np.nan, 0.0],
          index=pd.to_datetime(
              [
                  "2014-01-01",
                  "2014-01-02",
                  "2014-01-02",
                  "2014-01-03",
                  "2014-01-03",
                  "2014-01-04",
              ]
          ),
          columns=["value"],
      )
      regularized_data = regularization.regularize_series(test_series)
      self.assertLen(regularized_data.values, 4)
      self.assertEqual(regularized_data.values[0, 0], 1)
      self.assertEqual(regularized_data.values[1, 0], 5)
      self.assertTrue(np.isnan(regularized_data.values[2, 0]))
      self.assertEqual(regularized_data.values[3, 0], 0)
  
file_path: probability/tensorflow_probability/python/sts/regularization_test.py
imports: import datetime
  from absl.testing import parameterized
  import numpy
  import pandas
  from tensorflow_probability.python.internal import test_util
  from tensorflow_probability.python.sts import regularization
label_desc: Use image node_id 4 for calling the RegularizationTest obj's underlying member method code with example usage: obj.test_values_at_duplicate_indices_are_summed() without return types