code: def setUp(self):
      self._metric = Metric("test")
      self._mean = RunningMean("test")
      self._cache = [
          torch.Tensor([1.0]),
          torch.Tensor([1.5]),
          torch.Tensor([2.0]),
      ]
      self._target = 1.5
  
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 1 for calling the TestRunningMean obj's underlying member method code with example usage: obj.setUp() without return types