如何在动态Django ModelChoiceField中设置初始值?

I'm trying to create a simple page versioning system for a website. I want to be able to pass a page into a form, which points to all of the versions related to the page, and have the form dropdown contain all of the versions for that page, and make the initial page version the ideal version when it is initialized in the view. So far, the form will fill with all of the versions for the page, but not select the ideal version as the initial item.I'm trying to create a simple page versioning s