code: def handle_webhook_event(self, environ, url, params):
          
          for handler in self.events["webhook"]:
              urlpattern = handler.event.args["urlpattern"]
              if not urlpattern or match(urlpattern, url):
                  response = handler(self, environ, url, params)
                  if response:
                      return response
docs: Webhook handler - each handler for the webhook event
          takes an initial pattern argument for matching the URL
          requested. Here we match the URL to the pattern for each
          webhook handler, and bail out if it returns a response.