Initalizes the application with the extension.
        
        :param app: The Flask application object.

def init_app(self, app):
        '''Initalizes the application with the extension.
        
        :param app: The Flask application object.
        '''
        self.app = app
        self._session_conf = app.config.get('BEAKER_SESSION', {
            'session.type': 'file',
            'session.data_dir': '/tmp/session/data',
            'session.lock_dir': '/tmp/session/lock'
        })
        app.wsgi_app = SessionMiddleware(app.wsgi_app, self._session_conf)
        app.session_interface = BeakerSessionInterface()