text: class List(list): pass
  
  from itertools import product
  
  class Solution:
      def letterCombinations(self, digits: str) -> List[str]:
          if not digits: return []
          phone = {
              "2" : "abc",
              "3" : "def",
              "4" : "ghi",
              "5" : "jkl",
              "6" : "mno",
              "7" : "pqrs",
              "8" : "tuv",
              "9" : "wxyz"
          }
          return list(map("".join,product(*(phone[x] for x in digit))))
  
  
  
  
  s = Solution()
  digit = "23"
  print(s.letterCombinations(digit))