Username, the idea is to check that the username is not in use. So I use coll.findOne to search an user profile with that username (the database implementation is using mongodb). coll.findOne is an asynchronous operation, it needs await. Long story short, I tried to use this where the commented line:Function implicitly has return type 'any' because it does not have a return type annotation and is referenced directly or indirectly in one of its return expressions.ts(7024)Schema.filterEffect with that error.