public static function globalMappings($mappings = null) {
        if (self::$globalMappings === null) {
            self::$globalMappings = [];
        }

        if (is_array($mappings)) {
            $mappings = array_change_key_case($mappings);

            self::$globalMappings = array_replace(
                self::$globalMappings,
                $mappings
            );
        }

        return self::$globalMappings;
    }