@Override
        public boolean add(PermissionAttachment attachment) {
            if (LuckPermsPermissible.this.hookedAttachments.stream().anyMatch(at -> at.getSource() == attachment)) {
                return false;
            }

            new LuckPermsPermissionAttachment(LuckPermsPermissible.this, attachment).hook();
            return true;
        }
A fake set to be injected into the superclass. This implementation simply
proxies calls back to this permissible instance.

Some (clever/dumb??) plugins attempt to add/remove/query attachments using reflection.

An instance of this map is injected into the super instance so these plugins continue
to work with LuckPerms.
nukkit/src/main/java/me/lucko/luckperms/nukkit/inject/permissible/LuckPermsPermissible.java