Update:
The example above works when you trigger navigation from the top-level form (MainForm in the video example). But what happens if you want to trigger the navigation from one of the inner panels (Form1 and Form2 in our example)?
The answer is that you can use the get_open_form() function to get a reference to the current top-level form. You can then get at its methods and components. Eg:
new_page = Form2()
get_open_form().content_panel.clear()
get_open_form().content_panel.add_component(new_page)
You can find this information in the reference documentation here.