protected function getFilterResolver(string $filter): array
    {
        $class = $filter;
        $method = 'filter';

        $position = \strpos($filter, '@');

        if ($position === 0) {
            $method = 'filter'.\ucwords(\substr($filter, 1));

            return [$this, $method];
        }

        if ($position !== false) {
            list($class, $method) = \explode('@', $filter, 2);
        }

        return $this->makeFilterResolver($class, $method);
    }