Missing Ranges Python Solution with Tests

lcpy gen -n 163   # by problem number
lcpy gen -s missing_ranges   # by problem name

Input: nums = [0,1,3,50,75], lower = 0, upper = 99
Output: [[2,2],[4,49],[51,74],[76,99]]
Explanation: The ranges are:
[2,2]
[4,49]
[51,74]
[76,99]

Input: nums = [-1], lower = -1, upper = -1
Output: []
Explanation: There are no missing ranges since there are no missing numbers.

class Solution:
    # Time: O(n)
    # Space: O(1)
    def find_missing_ranges(self, nums: list[int], lower: int, upper: int) -> list[list[int]]:
        ranges: list[list[int]] = []
        prev = lower - 1
        for i in range(len(nums) + 1):
            curr = nums[i] if i < len(nums) else upper + 1
            if curr - prev >= 2:
                ranges.append([prev + 1, curr - 1])
            prev = curr
        return ranges