Remember Ren'Py loads files in ASCII order - so, if you've got 01_truncate_text.rpy inside a folder, it'll run based on the folder name.
Aka something like game/backend/01_truncate_text.rpy runs AFTER game/accessibility.rpy (so you couldn't use truncate_text inside accessibility.rpy).
I did request a special lib folder for the next version of Ren'Py, but at the moment your best bet is putting external libraries that need to run first inside a folder called something like 01_libraries/ so they run before your other files.
