Admin message error

When im uploading admin-message.php in the /wp-content/mu-plugins/ i get this error

Fatal error: Cannot redeclare admin_message_output() (previously declared in /home/sexabulo/domains/webfeminin.com/wp-content/mu-plugins/admin-message.php:39) in /home/sexabulo/domains/webfeminin.com/wp-content/plugins/admin-message-1.0.8/admin-message.php on lin