How to fetch Doctype values changed on client side


I want to send email to users who are removed from projects “project User” list.

For that, I need to compare user list in the database and updated users list for that.

I have written function on “before_insert” hook on Project doctype in a custom app. Fetching database users from frappe.get_all() method. But don’t know how to fetch users updated at the client side

Please see this documentation. Look for the Child Table Triggers section