private void hopperHandler(Hopper hopper, ItemStack item, Cancellable event) {
        Set<Matcher> matchers = plugin.findSign(hopper.getLocation().getBlock());

        if (matchers != null) {
            for (Matcher matcher : matchers) {
                if (matcher.match(item)) {
                    return;
                }
            }
            event.setCancelled(true);
        }
    }