I have an experiment with multiple timeouts. if the participant times-out, I want them to jump to a specific page at the end of the experiment. Is there a way I can easily make a default is_displayed function for all the pages in my experiment?

You can use inheritance. For more advanced uses, consider using my 𝐝𝐫𝐲𝐩𝐚𝐠𝐞 package.

Both methods are described here: https://gitlab.com/gr0ssmann/drypage

It's likely that the simple method outlined below "The problem" is sufficient for your application and you don't actually need 𝐝𝐫𝐲𝐩𝐚𝐠𝐞.