What algorithm is being used for smoothing by the pid controller?

Just for reference: Klipper with MPC
Dunno if there are any real world advantages or just added complexity, at least it sounds nice at the first impression.
This is the corresponding Marlin PR: https://github.com/MarlinFirmware/Marlin/pull/23751 (and MPC tuning improvements by tombrazier · Pull Request #23984 · MarlinFirmware/Marlin · GitHub)