Please solve the programming task below using a self-contained code snippet in a markdown code block.

A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers.
Given a string s, return true if it is a palindrome, or false otherwise.
 
Please complete the following python code precisely:
```python
class Solution:
    def isPalindrome(self, s: str) -> bool:
```