class Artist(Base):

    def add_reviews(self, review_ids):
        sess = object_session(self)
if isinstance(review_ids, int):
    review_ids = [review_ids]
sess.execute(Review.__table__.update().values(artist_id=self.artist_id).
    where(Review.id.in_(review_ids)))
sess.refresh(self)
review_ids = [123, 556, 998, 667, 111]
artist.add_reviews(review_ids)
review_id = 333
artist.add_reviews(review_id)
SQLAlchemy: add a relationship using id instead of object?