private LuckPermsSubscriptionMap inject() throws Exception {
        Objects.requireNonNull(PERM_SUBS_FIELD, "PERM_SUBS_FIELD");
        PluginManager pluginManager = this.plugin.getBootstrap().getServer().getPluginManager();

        Object map = PERM_SUBS_FIELD.get(pluginManager);
        if (map instanceof LuckPermsSubscriptionMap) {
            if (((LuckPermsSubscriptionMap) map).plugin == this.plugin) {
                return null;
            }

            map = ((LuckPermsSubscriptionMap) map).detach();
        }

        //noinspection unchecked
        Map<String, Set<Permissible>> castedMap = (Map<String, Set<Permissible>>) map;

        // make a new subscription map & inject it
        LuckPermsSubscriptionMap newMap = new LuckPermsSubscriptionMap(this.plugin, castedMap);
        PERM_SUBS_FIELD.set(pluginManager, newMap);
        return newMap;
    }
Injects a {@link LuckPermsSubscriptionMap} into the {@link PluginManager}.
nukkit/src/main/java/me/lucko/luckperms/nukkit/inject/server/InjectorSubscriptionMap.java