private static function schemaCache(...$args)
    {
        if (count($args) == 1) {
            $key = array_pop($args);
            if (isset(static::$schema_cache[$key])) {
                return static::$schema_cache[$key];
            }

            return false;
        }

        list($key, $value) = $args;

        static::$schema_cache[$key] = $value;
    }