I am having an issue with the Happy Number challenge.  My code works when I use 7 as a custom test case, but fails the test when I go to submit my code.  Any insight would be appreciated.  Here\'s my code:\n\n```class Solution(object):\n    def isHappy(self, n, num_set= set()):\n        """\n        :type n: int\n        :rtype: bool\n        """\n        if n==1:\n            return True\n        \n        else:\n            happy_str=0\n            for num in str(n):\n                happy_str += (int(num) ** 2)\n\n        if happy_str in num_set:\n            return False\n\n        num_set.add(happy_str)\n        return self.isHappy(happy_str, num_set)```

I am having an issue with the Happy Number challenge.  My code works when I use 7 as a custom test case, but fails the test when I go to submit my code.  Any in