Sentinel Reminder::exists() error

Hi Im using Cartalyst/Sentinel for a login system everything work fine but this Reminder::exists($user) function giving this error Argument 1 passed to Cartalyst\Sentinel\Reminders\IlluminateReminderRepository::exists() must implement interface cartalyst\Sentinel\Users\UserInterface

code is same as given on their example page. http://ift.tt/29t2MMC

$user = Sentinel::findById($credentials);

//dd($user); // this dump user return collection object of user

 $reminder = Reminder::exists( $user );

via Chebli Mohamed