code: def check_sla(self, sla, diff_metric):
      
      try:
        if sla.display is '%':
          diff_val = float(diff_metric['percent_diff'])
        else:
          diff_val = float(diff_metric['absolute_diff'])
      except ValueError:
        return False
      if not (sla.check_sla_passed(diff_val)):
        self.sla_failures += 1
        self.sla_failure_list.append(DiffSLAFailure(sla, diff_metric))
      return True
docs: Check whether the SLA has passed or failed