protected function resolve_excludes($variable, $default = null) {
        $setting = $default;
        if (is_array($this->{$variable}) or $this->{$variable} === true) {
            $setting = $this->{$variable};
        } else {
            foreach ($this->parent_configs as $parent_config) { // the immediate parent first, base last
                if (!isset($parent_config->{$variable})) {
                    continue;
                }
                if (is_array($parent_config->{$variable}) or $parent_config->{$variable} === true) {
                    $setting = $parent_config->{$variable};
                    break;
                }
            }
        }
        return $setting;
    }