How to get data from message_new event object? VK API BOT?

Question

Python

Help with code. I need to get the ref and ref_source parameters, but I can't figure out how to get data from the message_new event object. I've already rummaged through all the Vk Api documentation but never got close to an answer. It is impossible to get ref and ref_source through Event.

Here is the text from the documentation:
"... but also pass arbitrary ref and ref_source parameters in such a link, which will be returned in the message object in the message_new Callback API or Bots Long Poll API event, if the user starts or continues the conversation via a link like vk. me".