public function group(string $prefix, callable $callback): Group
    {
        $group = new Group($prefix, $callback);
        $this->mount($group);
        return $group;
    }
public function group(string $prefix, callable $callback): Group
    {
        $group = new Group($prefix, $callback);
        $this->mount($group);
        return $group;
    }
@param string $prefix
@param callable $callback

@return Group