Please help me with this python question, thank you very much!

lef factorial(n: int) -> int: "Compute a factorial. :param n: The number to factorialize :return: the factorial of n >>> factorial (0) 1 >>> factorial(1) 1 >>> factorial(5) 120 >>> for i in range(6,20): factorial(i) 720 5040 121645100408832000 >>> factorial(-1) # check validity of n: if not isinstance(n, int) or n >> ValueError +ELLIPSIS None # doctest: +ELLIPSIS 40320 doctest: ELLIPSIS