Python 3.7 builtins.NameError

现在我正在学习一些基本的东西,比如list等等,但是我在编写代码时遇到了一个问题:

from typing import List


def greatest_difference(nums1: List[int], nums2: List[int]) -> int:
    """Return the greatest absolute difference between numbers at
    corresponding positions in nums1 and nums2.

    Precondition: len(nums1) == len(nums2) and nums1 != []

    >>> greatest_difference([1, 2, 3], [6, 8, 10])
    7
    >>> greatest_difference([1, -2, 3], [-6, 8, 10])
    10
    """
difference = 0
diff_over_term = 0
for i in range(len(nums1)):
    diff_over_term = abs(nums1[i] - nums2[i])
if diff_over_term > difference:
        difference = diff_over_term
print(difference)

因为某些原因,它说

builtins.NameError:名称 nums1 未定义

我试着玩缩进游戏,但没用。