Right here. 
Two big issues:
1. It skips making any associations if `belongs_to` references something polymorphic
2. It didn't know how to get the `depends_on` `table_name` when the association was polymorphic because `association.table_name` would raise a method not found error

I thought my solution would have to modify the `id_map`, but it actually didn't. I deleted a lot of my initial code when I realized I could go on without it.