private function filterPrefixer(array &$filter)
    {
        foreach ($filter as &$child) {
            if (\array_key_exists('property', $child)
                && (false === \strpos($child['property'], $this->source . '.'))
                && $this->fieldExists($child['property'])
            ) {
                $child['property'] = $this->source . '.' . $child['property'];
            }

            if (\array_key_exists('children', $child)) {
                $this->filterPrefixer($child['children']);
            }
        }
    }