How to use the seleniumbase.fixtures.js_utils.add_css_style function in seleniumbase

def activate_bootstrap(driver):
    """ Allows you to use Bootstrap Tours with SeleniumBase
        http://bootstraptour.com/
    """
    bootstrap_tour_css = constants.BootstrapTour.MIN_CSS
    bootstrap_tour_js = constants.BootstrapTour.MIN_JS

    verify_script = ("""// Verify Bootstrap Tour activated
                     var tour2 = new Tour({
                     });""")

    backdrop_style = style_sheet.bt_backdrop_style
    js_utils.add_css_style(driver, backdrop_style)
    js_utils.wait_for_ready_state_complete(driver)
    js_utils.wait_for_angularjs(driver)
    for x in range(4):
        js_utils.activate_jquery(driver)
        js_utils.add_css_link(driver, bootstrap_tour_css)
        js_utils.add_js_link(driver, bootstrap_tour_js)
        time.sleep(0.1)
        for x in range(int(settings.MINI_TIMEOUT * 2.0)):
            # Bootstrap needs a small amount of time to load & activate.
            try:
                driver.execute_script(verify_script)
                time.sleep(0.05)
                return
            except Exception:
                time.sleep(0.15)
    js_utils.raise_unable_to_load_jquery_exception(driver)

def add_css_style(self, css_style):
        js_utils.add_css_style(self.driver, css_style)

shepherd_js = constants.Shepherd.MIN_JS
    sh_theme_arrows_css = constants.Shepherd.THEME_ARROWS_CSS
    sh_theme_arrows_fix_css = constants.Shepherd.THEME_ARR_FIX_CSS
    sh_theme_default_css = constants.Shepherd.THEME_DEFAULT_CSS
    sh_theme_dark_css = constants.Shepherd.THEME_DARK_CSS
    sh_theme_sq_css = constants.Shepherd.THEME_SQ_CSS
    sh_theme_sq_dark_css = constants.Shepherd.THEME_SQ_DK_CSS
    tether_js = constants.Tether.MIN_JS
    spinner_css = constants.Messenger.SPINNER_CSS
    sh_style = style_sheet.sh_style_test
    backdrop_style = style_sheet.sh_backdrop_style

    activate_bootstrap(driver)
    js_utils.wait_for_ready_state_complete(driver)
    js_utils.wait_for_angularjs(driver)
    js_utils.add_css_style(driver, backdrop_style)
    js_utils.wait_for_ready_state_complete(driver)
    js_utils.wait_for_angularjs(driver)
    for x in range(4):
        js_utils.add_css_link(driver, spinner_css)
        js_utils.add_css_link(driver, sh_theme_arrows_css)
        js_utils.add_css_link(driver, sh_theme_arrows_fix_css)
        js_utils.add_css_link(driver, sh_theme_default_css)
        js_utils.add_css_link(driver, sh_theme_dark_css)
        js_utils.add_css_link(driver, sh_theme_sq_css)
        js_utils.add_css_link(driver, sh_theme_sq_dark_css)
        js_utils.add_js_link(driver, tether_js)
        js_utils.add_js_link(driver, shepherd_js)
        time.sleep(0.1)
        for x in range(int(settings.MINI_TIMEOUT * 2.0)):
            # Shepherd needs a small amount of time to load & activate.
            try: