code: def replace_policy(self, scaling_group, policy, name,
              policy_type, cooldown, change=None, is_percent=False,
              desired_capacity=None, args=None):
          
          policy_id = utils.get_id(policy)
          group_id = utils.get_id(scaling_group)
          uri = "/%s/%s/policies/%s" % (self.uri_base, group_id, policy_id)
          body = self._create_policy_body(name=name, policy_type=policy_type,
                  cooldown=cooldown, change=change, is_percent=is_percent,
                  desired_capacity=desired_capacity, args=args)
          resp, resp_body = self.api.method_put(uri, body=body)
docs: Replace an existing policy. All of the attributes must be specified. If
          you wish to delete any of the optional attributes, pass them in as
          None.