protected function getRequired($scope = 'Index', $method = Doozr_Http::REQUEST_METHOD_GET)
    {
        // prepare storage on method/verb level
        if (!isset($this->required[$method])) {
            return [];
        }

        // prepare storage on scope level
        if (!isset($this->required[$method][$scope])) {
            return [];
        }

        return $this->required[$method][$scope];
    }