Valid Palindrome III

class Solution:

    def helper(self, s, start, end):
        # base cases
        if start >= end:
            self.cache[(start, end)] = 0
            return 0
        if (start, end) in self.cache:
            return self.cache[(start, end)]

        if s[start] == s[end]:
            self.cache[(start, end)] = self.helper(s, start+1, end-1)
        else:
            remove_start = 1 + self.helper(s, start+1, end)
            remove_end = 1 + self.helper(s, start, end-1)
            self.cache[(start, end)] = min(remove_start, remove_end)

        return self.cache[(start, end)]

    def isValidPalindrome(self, s: str, k: int) -> bool:
        self.cache = {}
        return self.helper(s, 0, len(s)-1) <=k