The functionality you need is in the [sorter] module.
Call [sorter::sort_file_contents] with the file contents and the sorter options.
The [parser] module contains the functions to parse the classes from a file.
The [parser::parse_classes_from_file] function will return a HashMap<String, usize> with the classes and their order.
You can use this to create a custom sorter. Using this customer sorter you can call [sorter::sort_file_contents].