I am trying to write a query on datalemur but my solution is not getting accepted

Throwing me error : function round(double precision, integer) does not exist (LINE: 4)

Question : Link

My query not accepted :

SELECT
    EXTRACT(MONTH FROM submit_date) AS mth,
    product_id                      AS product,
    round((AVG(stars)),
          2)                        AS avg_stars
FROM
    reviews
GROUP BY
    EXTRACT(MONTH FROM submit_date),
    product_id
ORDER BY
    mth,
    product;

What is the mistake I am making could you help me to identify it.