input: Write a python function to check if a given string is a palindrome, ignoring non-alphabetic characters and case sensitivity.
  assert isPalindrome("A man, a plan, a canal, Panama!") == True
  assert isPalindrome("No lemon, no melon") == True
  assert isPalindrome("Hello, World!") == False
output: def isPalindrome(s: str) -> bool:
      cleaned = ''.join(c.lower() for c in s if c.isalpha())
      return cleaned == cleaned[::-1]