python flask web:TypeError TypeError: 'bool' object is not callable

The error occurs: @auth.before_app_request def before_request():

if current_user.is_authenticated() \
        and not current_user.confirmed \
        and request.endpoint[:5] != 'auth.' \
        and request.endpoint != 'static':
    return redirect(url_for('auth.unconfirmed'))

The debugger indicates that "if current_user.is_authenticated() \" leads to the error.Please help me!