What's the 'navigation_utils' in client.py?

[zhaolixin0726]

Recently, I need to use your method to generate har files. But I add a user_agent to emulate iPhone.
In ChromeRDPWebsocket's _init function, added:
self.user_agent = "Mozilla/5.0 (iPhone; CPU iPhone OS 9_1 like Mac OS X) AppleWebKit/601.1.46 (KHTML, like Gecko) Version/9.0 Mobile/13B143 Safari/601.1"
Then opened the codes in def on_open, such as

def on_open(self, ws):

    self.navigate_to_page('about:blank')

    self.enable_network_tracking()

    self.enable_page_tracking()

    self.clear_cache()

    if self.user_agent is not None:

        navigation_utils.set_user_agent(self.ws, self.user_agent)

    if self.screen_size_config is not None:

        navigation_utils.set_device_screen_size(self.ws, self.screen_size_config, 

self.device_configuration['page_id'])

But 'navigation_utils' was not found and definited.
Can you tell me what's the navigation_utils?