input: Write a function to check if a given string is a palindrome by removing non-alphanumeric characters and comparing the reversed version of the string.
  assert is_palindrome("A man, a plan, a canal, Panama!") == True
  assert is_palindrome("Was it a car or a cat I saw?") == True
  assert is_palindrome("No 'x' in Nixon") == True
  assert is_palindrome("Hello, World!") == False
output: def is_palindrome(s):
      import re
      cleaned = re.sub(r'[^A-Za-z0-9]', '', s).lower()
      return cleaned == cleaned[::-1]