pyRevit c# .net lib reference

I’m trying to bring some old-ish (2017 last updated, feels like yesterday) C# Code we have back to life in pyrevit.

I’m sure this is going to be an easy one for anyone with good .net knowledge, unfortunately my skill Set with C# and .net generally is pretty poor, but I can just about navigate a script.

I’m stuck on the following error:

error CS0103: The name 'DocUtils' does not exist in the current context (x3 similar)

I’ve tried loading the Utils files into my normal pyRevit Lib folder, and also as a subfolder of the main .pushbutton folder but no luck. am I barking up the wrong tree/ missing something easy here? or do .net scripts need to be self-contained to execute in pyRevit?