Similar_users / get_user_representations

Hi, I just some develop customizing recommend model based on Lightfm.
it almost same things(movielense), but if input data don`t have user_id and only have purchase record(like movie-title, movie-rating),
how i predict only have purchase_record?
i want find out similar user_id from purchase record.
if any tiny tips you have or want more info, i waiting always on this comments

Start by clarifying whether the request is for predicting with purchase records that lack user IDs or for finding similar users from those records. The issue names no files, tests, or entry points, so the scope and a concrete definition of done need to be established before implementation.

Written by the indexing model from the issue text.