Function bus_watch_name 

pub fn bus_watch_name<NameAppeared, NameVanished>(
    bus_type: BusType,
    name: &str,
    flags: BusNameWatcherFlags,
    name_appeared: NameAppeared,
    name_vanished: NameVanished,
) -> WatcherId
where
    NameAppeared: Fn(DBusConnection, &str, &str) + 'static,
    NameVanished: Fn(DBusConnection, &str) + 'static,