destroy() {
        if (this.subs) {
            // clean subscriptions to avoid reconnections
            this.subs.forEach((subDestroy) => subDestroy());
            this.subs = undefined;
        }
        this.io["_destroy"](this);
    }
Called upon forced client/server side disconnections,
this method ensures the manager stops tracking us and
that reconnections don't get triggered for this.

@private