fmn is a family of systems to manage end-user notifications triggered by fedmsg, the Fedora FEDerated MESsage bus.
This module contains the set of "rules" fmn uses to process messages.
There is a parental placeholder repo with some useful information you might want to read through, like an overview, a little architecture diagram.
Find development instructions here: https://github.com/fedora-infra/fmn/#hacking