code: def get_total_time(self):
          
          first_step = self.steps[0]
          last_step = self.steps[-1]
          seconds = self.history[last_step]["__timestamp__"] \
                    - self.history[first_step]["__timestamp__"]
          return datetime.timedelta(seconds=seconds)
docs: Returns the total period between when the first and last steps
          where logged. This usually correspnods to the total training time
          if there were no gaps in the training.