input: Write a python function to check if a given string is a palindrome.
  assert isPalindrome('racecar') == True
  assert isPalindrome('hello') == False
  assert isPalindrome('A man a plan a canal Panama') == True
output: def isPalindrome(s: str) -> bool:
      s = ''.join(c.lower() for c in s if c.isalnum())
      return s == s[::-1]