input: Write a Python function:
  
  def sum_of_subsequence_powers(elements: List[int], k: int) -> int:
      """
      Given an integer array elements with n items, and a positive integer k, the task is to compute the sum of the powers of all subsequences of elements of length k.
  
      The power of a subsequence is defined as the smallest absolute difference between any two elements in that subsequence.
  
      The result should be returned modulo 10^9 + 7.
  
      Examples:
      >>> elements = [1,2,3,4], k = 3
      4
      >>> elements = [2,2], k = 2
      0
      >>> elements = [4,3,-1], k = 2
      10
  
      Constraints:
      2 <= n == elements.length <= 50
      -10^8 <= elements[i] <= 10^8
      2 <= k <= n
      """
output: def sum_of_subsequence_powers(elements: List[int], k: int) -> int:
      from itertools import combinations
      MOD = 10**9 + 7
  
      def power(subseq):
          min_diff = float('inf')
          for i in range(1, len(subseq)):
              min_diff = min(min_diff, abs(subseq[i] - subseq[i-1]))
          return min_diff
  
      elements.sort()
      total_power = 0
      for subseq in combinations(elements, k):
          total_power += power(subseq)
          total_power %= MOD
          
      return total_power