def _assert_token(connection_banner, driver):
    """Poll for backend to be up.

    Args:
        connection_banner: AppHarness instance.
        driver: Selenium webdriver instance.
    """
    ss = SessionStorage(driver)
    assert connection_banner._poll_for(lambda: ss.get("token") is not None), (
        "token not found"
    )
Poll for backend to be up.

    Args:
        connection_banner: AppHarness instance.
        driver: Selenium webdriver instance.
    
tests/integration/test_connection_banner.py