In this example, the "get_session_user" function is called to retrieve the current user from the session. The function is imported from the session.php file which is assumed to contain the function. The retrieved user is then used to display a welcome message. Therefore, it is not clear which package/library the "get_session_user" belongs to as it is not a standard PHP function. It can be a custom function written by the developer or taken from an external library/package.