code: def process(self, *args):
      super(_TimerMetric, self).process(*args)
      dt = time.time() - self.t
      self.t = time.time()
      return dt
  
imports: from __future__ import print_function
  import sys
  import time
  from torchbearer.callbacks import Callback
  import torchbearer
  from torchbearer.metrics import Metric
label_desc: Use image node_id 2 for calling the _TimerMetric obj's underlying member method code with example usage: obj.process() and returns: dt