code: def test_empty_methods(self):
      metric = RunningMetric("test")
      self.assertRaises(
          NotImplementedError, lambda: metric._step(["test"]) is None
      )
      self.assertRaises(
          NotImplementedError,
          lambda: metric._process_train(["test"]) is None,
      )
  
imports: import unittest
  from mock import Mock, call
  from torchbearer.metrics import RunningMean, Metric, RunningMetric, Mean, Std, Var
  import torch
label_desc: Use image node_id 4 for calling the TestRunningMetric obj's underlying member method code with example usage: obj.test_empty_methods() without return types