- mutable primary key support is added. primary key columns can be

- mutable primary key support is added. primary key columns can be
changed freely, and the identity of the instance will change upon
flush. In addition, update cascades of foreign key referents (primary
key or not) along relations are supported, either in tandem with the
database's ON UPDATE CASCADE (required for DB's like Postgres) or
issued directly by the ORM in the form of UPDATE statements, by setting
the flag "passive_cascades=False".