class_docstr: Tests the main functions in the library.
code: def test_aggregate_metrics(self):
      self.assertEqual(metrics.aggregate_median(self._x), 1.5)
      self.assertEqual(metrics.aggregate_mean(self._x), 1.5)
      self.assertEqual(metrics.aggregate_iqm(self._x), 1.5)
  
      self.assertEqual(metrics.aggregate_median(self._y), 2)
      self.assertEqual(metrics.aggregate_mean(self._y), 2)
      self.assertEqual(metrics.aggregate_iqm(self._y), 2)
      self.assertAlmostEqual(
          metrics.probability_of_improvement(self._x, self._y), 1 / 3
      )
  
imports: from absl.testing import absltest
  import numpy
  import rliable.metrics
label_desc: Use image node_id 2 for calling the MetricsTest obj's underlying member method code with example usage: obj.test_aggregate_metrics() without return types