Function run 

pub fn run(
    config: &Config,
    dirs: &Dirs,
    here: &dyn Fn(&Account) -> bool,
    progress: &mut dyn FnMut(&Progress),
    cancel: &Cancel,
) -> Result<(Update, Summary), LearnError>

“Train now”: the corpus brought up to date from every account (each password as the sync uses it; a Microsoft one only with your consent, consent, which the window keeps first), then train with your thresholds. here: whether an account is still in the configuration (corpus::update). For the window: run it on a thread of its own; progress says each step, cancel stops it at the next.