decode way

#https://leetcode.com/problems/decode-ways/
from functools import lru_cache

class Solution:
    @lru_cache(maxsize=None)
    def numDecodingsHelper(self, s, index) -> int:
        if (index == len(s)):
            return 1
        if (s[index] == "0"):
            return 0
        if (index == len(s) - 1):
            return 1
        oneCount = self.numDecodingsHelper(s, index + 1)
        twoCount = 0
        twoDigit = int(s[index] + s[index+1])
        if (twoDigit >= 10 and twoDigit <= 26):
            twoCount =  self.numDecodingsHelper(s, index + 2)
        return oneCount + twoCount

    def numDecodings(self, s: str) -> int:
        return self.numDecodingsHelper(s, 0)