code: def delete_webhook(self, scaling_group, policy, webhook):
          
          uri = "/%s/%s/policies/%s/webhooks/%s" % (self.uri_base,
                  utils.get_id(scaling_group), utils.get_id(policy),
                  utils.get_id(webhook))
          resp, resp_body = self.api.method_delete(uri)
          return None
docs: Deletes the specified webhook from the specified policy.