Returns an iterator over all entity states held by this Unit Of Work.

def iterator(self):
        """
        Returns an iterator over all entity states held by this Unit Of Work.
        """
        # FIXME: There is no dependency tracking; objects are iterated in
        #        random order.
        for ent_cls in list(self.__entity_set_map.keys()):
            for ent in self.__entity_set_map[ent_cls]:
                yield EntityState.get_state(ent)