Fatal error: Uncaught Error: Class 'rcube_addressbook' not found in /usr/local/www/roundcube/plugins/example_addressbook/example_addressbook_backend.php:10
Stack trace:
#0 /usr/local/www/roundcube/plugins/example_addressbook/example_addressbook.php(3): require_once()
#1 {main}
thrown in /usr/local/www/roundcube/plugins/example_addressbook/example_addressbook_backend.php on line 10