code: def add_rule(self, rule_class, target_class=_Nothing):
          
          if isinstance(target_class, Iterable):
              for cls in target_class:
                  self._rules[cls] = rule_class
          else:
              self._rules[target_class] = rule_class
docs: Adds an authorization rule.
  
          :param rule_class: a class of authorization rule.
          :param target_class: (optional) a class
              or an iterable with classes to associate the rule with.