/**
* Return whether cache is valid or invalid
*
* @param string $key Cache key
* @param int $modified_time Unix time of data modified.
* If stored time is older then modified time, the data is invalid.
* @return bool Return true on valid or false on invalid.
*/
public function isValid($key, $modified_time = 0)
{
return Rhymix\Framework\Cache::exists($key);
}
