input: def is_palindrome(s: str) -> bool:
      """ Check if given string is a palindrome. A palindrome is a string that reads the same forwards and backwards.
      >>> is_palindrome("racecar")
      True
      >>> is_palindrome("hello")
      False
      >>> is_palindrome("A man a plan a canal Panama")
      True
      """
      s = ''.join(filter(str.isalnum, s)).lower()
      return s == s[::-1]
output:     s = ''.join(filter(str.isalnum, s)).lower()
      return s == s[::-1]