Here's pure python code for experimentation:

    from marshal import dumps, loads

    def marshal_set(s):
        return dumps(sorted(s, key=dumps))

    def unmarshal_set(m):
        return frozenset(loads(m))

    def test(s):
        assert unmarshal_set(marshal_set(s)) == s
        
    test({("string", 1), ("string", 2), ("string", 3)})