code: def test_reset(self):
      state = {
          torchbearer.CALLBACK_LIST: torchbearer.callbacks.CallbackList(
              []
          )
      }
  
      timer = TimerMetric()
      self.assertTrue(
          state[torchbearer.CALLBACK_LIST].callback_list == []
      )
      timer.reset(state)
      self.assertIsInstance(
          state[torchbearer.CALLBACK_LIST].callback_list[0], TimerMetric
      )
  
      timer.reset(state)
      self.assertTrue(
          len(state[torchbearer.CALLBACK_LIST].callback_list) == 1
      )
  
file_path: torchbearer/tests/metrics/test_timer.py
imports: from unittest import TestCase
  from mock import Mock, MagicMock, patch
  import torchbearer
  from torchbearer.metrics.timer import TimerMetric, _TimerMetric
label_desc: Use image node_id 4 for calling the TestTimer obj's underlying member method code with example usage: obj.test_reset() without return types