How do models get synced in Frappe?

we usually create a doctype and it make sql alter db and write a json file which works as a migration file like in django how does the front end renders the changes apples from the model is it going to read the form fields from json file and rendering it ? where is this part in frappe code ? is it this one frappe/ at master · frappe/frappe · GitHub

Models (doctypes) get synced like all other models from the JSON files everytime you migrate. And the controller manages the schema changes.