code: def test_eval(self):
      my_mock = Metric("test")
      my_mock.eval = Mock(return_value=None)
      metric = MetricList([my_mock])
      metric.eval()
      self.assertEqual(my_mock.eval.call_count, 1)
  
imports: import unittest
  from mock import Mock
  from torchbearer.metrics import MetricList, Metric, MetricTree, AdvancedMetric
label_desc: Use image node_id 8 for calling the TestMetricList obj's underlying member method code with example usage: obj.test_eval() without return types