Gradebook

I am writing a new grade import plugin, and I am seeing the use of importcodes, the grade_import_newitem and grade_import_values tables, and grade_import_commit.

I have a pretty good idea of what it all does, but is this system (/grade/import/lib.php) documented from a high-level anywhere? Should I be using this stuff for my grade importer? Do I have to use it?

Thanks