Validate product codes

A valid product code is three capital letters, a dash, and three digits, like BRD-001. Write valid_codes(codes) that returns the list of valid codes from the input, in order.

valid_codes(["BRD-001", "brd-001", "BRD-01", "MLK-010", "BRD001"])  ->  ["BRD-001", "MLK-010"]

def valid_codes(codes):
    ...