docs: def _calculate_duration(start_time, finish_time):
      """Calculates how long it took to execute the testcase."""
      if not (start_time and finish_time):
          return 0
      start = datetime.datetime.fromtimestamp(start_time)
      finish = datetime.datetime.fromtimestamp(finish_time)
      duration = finish - start
  
      decimals = float(("0." + str(duration.microseconds)))
      return duration.seconds + decimals