code: def webhook():
      
      # When you first tell Nylas about your webhook, it will test that webhook
      # URL with a GET request to make sure that it responds correctly.
      # We just need to return the `challenge` parameter to indicate that this
      # is a valid webhook URL.
      if request.method == "GET" and "challenge" in request.args:
          print(" * Nylas connected to the webhook!")
          return request.args["challenge"]
  
      # Alright, this is a POST request, which means it's a webhook notification.
      # The question is, is it genuine or fake? Check the signature to find out.
      is_genuine = verify_signature(
          message=request.data,
          key=app.config["NYLAS_OAUTH_CLIENT_SECRET"].encode("utf8"),
          signature=request.headers.get("X-Nylas-Signature"),
      )
      if not is_genuine:
          return "Signature verification failed!", 401
  
      # Alright, we have a genuine webhook notification from Nylas!
      # Let's find out what it says...
      data = request.get_json()
      for delta in data["deltas"]:
          # Processing the data might take awhile, or it might fail.
          # As a result, instead of processing it right now, we'll push a task
          # onto the Celery task queue, to handle it later. That way,
          # we've got the data saved, and we can return a response to the
          # Nylas webhook notification right now.
          process_delta.delay(delta)
  
      # Now that all the `process_delta` tasks have been queued, we can
      # return an HTTP response to Nylas, to let them know that we processed
      # the webhook notification successfully.
      return "Deltas have been queued", 200
docs: When the Flask server gets a request at the `/webhook` URL, it will run
      this function. Most of the time, that request will be a genuine webhook
      notification from Nylas. However, it's possible that the request could
      be a fake notification from someone else, trying to fool our app. This
      function needs to verify that the webhook is genuine!