https://mpatacchiola.github.io/blog/2021/02/08/intro-variational-inference-2.html # https://en.wikipedia.org/wiki/Evidence_lower_bound https://chatgpt.com/c/68bde1aa-55a8-8321-9a10-f562db9c7b55 https://chatgpt.com/g/g-p-68bcc91a795c8191b02e92abaf3daa0c-tutorials/c/68bdef4a-014c-8331-831b-20411611b315 score function