sqlalchemy seems have no support for insert cte - postgresql

Question

By given table creation statement and query it's necessary to get old values before update:
CREATE TABLE IF NOT EXISTS products(
id INT GENERATED BY DEFAULT AS IDENTITY NOT NULL PRIMARY KEY,
product_id INT UNIQUE,
image_link CHARACTER VARYING NOT NULL,
additional_image_links CHARACTER VARYING[] NOT NULL
);
WITH temp AS (
INSERT INTO products(product_id, image_link, additional_image_links)
VALUES(1, 'http://www.e1xazm1ple1k113.com',ARRAY['http://www.examkple1113.com','http://www.example2.com'])
ON CONFLICT (product_id) DO UPDATE SET image_link = EXCLUDED.image_link, additional_image_links = EXCLUDED.additional_image_links
WHERE products.image_link != EXCLUDED.image_link OR products.additional_image_links != EXCLUDED.additional_image_links OR products.image_link != EXCLUDED.image_link
RETURNING id, image_link, additional_image_links
)
SELECT image_link, additional_image_links FROM products WHERE id IN (SELECT id FROM temp);
If conflict happens and new values conform criteria result is generated, however I need to use sqlalchemy machinery for it. Approximate but not working example:
def upsert(table, rows, constraint, update_cols):
query = insert(table).values(rows)
return query.on_conflict_do_update(
constraint=constraint,
set_={c: getattr(query.excluded, c) for c in update_cols},
where=getattr(table.c, "additional_image_link") != getattr(query.excluded, "additional_image_link"),
).cte("upsert")
Calling which produces the exception:
sesh = session(autocommit=False, autoflush=False, engine=DEFAULT)
sesh.execute(upsert(*args))
sqlalchemy.exc.ArgumentError: Executable SQL or text() construct expected, got <sqlalchemy.sql.selectable.CTE at 0x1042c3f10; upsert>.