Sum of Subsequence Widths Python Solution

lcpy gen -n 891   # by problem number
lcpy gen -s sum_of_subseq_widths   # by problem name

Input: nums = [2,1,3]
Output: 6
Explanation: The subsequences are [1], [2], [3], [2,1], [2,3], [1,3], [2,1,3].
The corresponding widths are 0, 0, 0, 1, 1, 2, 2.
The sum of these widths is 6.

Input: nums = [2]
Output: 0

class Solution:
    # Time: O(n log n)
    # Space: O(1)
    def sum_subseq_widths(self, nums: list[int]) -> int:
        mod = 10**9 + 7
        ordered = sorted(nums)
        total = 0
        n = len(ordered)
        pow2 = 1
        for i, value in enumerate(ordered):
            total += value * (pow2 - 1) - value * (pow(2, n - 1 - i, mod) - 1)
            total %= mod
            pow2 = pow2 * 2 % mod
        return total