public function postFieldNested(Closure $callback)
    {
        // To handle nested post fields we'll actually create a brand new query instance
        // and pass it off to the Closure that we have. The Closure can simply do
        // do whatever it wants to a post field then we will store it for compiling.
        $query = $this->newQuery();

        call_user_func($callback, $query);

        return $this->addNestedPostFieldQuery($query);
    }