code: def test_time_metric(self):
      metric = TimerMetric(10, 0, 1)
      assert metric.value() == 10
      metric = TimerMetric(10, 0, 2)
      assert metric.value() == 5
      metric2 = TimerMetric(10, 4, 5)
      # final start time 0
      # final end time 5
      # total processed = 20
      assert (metric + metric2).value() == 4
  
imports: import unittest
  from typing import Dict
  import torch
  import random
  from parlai.core.metrics import AverageMetric, SumMetric, FixedMetric, Metrics, GlobalAverageMetric, MacroAverageMetric, TimerMetric, aggregate_unnamed_reports, aggregate_named_reports, InterDistinctMetric, IntraDistinctMetric, FairseqBleuMetric
  from parlai.core.torch_classifier_agent import ConfusionMatrixMetric, WeightedF1Metric, AUCMetrics
  from parlai.core.torch_generator_agent import PPLMetric
  import parlai.utils.testing
label_desc: Use image node_id 4 for calling the TestAggregators obj's underlying member method code with example usage: obj.test_time_metric() without return types