The bridge configuration does not take effect

[yafeng-Soong]

When I passed ‘obfs4’ to the 'default_bridge_type' property of the TorBrowserDriver function, the browser was still directly connected to the Tor network. Do I need any special configuration to launch TorBrowserDriver with bridge?
Here is my code:

tor_process = launch_tbb_tor_with_stem(tbb_path=tbb_dir, torrc=torrc_dict)
with TorBrowserDriver(tbb_dir, tor_cfg=cm.USE_STEM, default_bridge_type='obfs4', pref_dict=ffpref, tbb_logfile_path='/dev/null') as driver:
        driver.load_url("https://check.torproject.org")
        print(driver.find_element_by("h1.on").text)
        print(driver.find_element_by(".content > p").text)
tor_process.kill()

I have tried both versions 11.0.14 and 11.5.4