python typing example

after set python.linting.mypyEnabled to true(not to sell you have Pylance in place) you are equipped with typing

import sys
from typing import Tuple, Union

global nums


def sum2(start: int, end: int, target: int) -> Union[Tuple[int, int], None]:
    seen = set()
    for i in range(start, end):
        n = nums[i]
        if target - n in seen:
            return (n, (2020 - n))
        else:
            seen.add(n)
    return None


if __name__ == "__main__":
    nums = sorted(map(int, sys.stdin))
    end = len(nums)
    for i, num in enumerate(nums):
        ret = sum2(i, end, 2020 - num)
        if ret is not None:
            print(num * ret[0] * ret[1])