The RowCreatedSignal class is accessible via the sqlobject.events module.
Note: this is not called when an instance is created from an existing database row.
Abstract classes can override this to customize issubclass().
This is invoked early on by abc.ABCMeta.__subclasscheck__(). It should return True, False or NotImplemented. If it returns NotImplemented, the normal algorithm is used. Otherwise, it overrides the normal algorithm (and the outcome is cached).
See the source for more information.