input: 
  def is_palindrome(s: str) -> bool:
      """
      Takes a string and indicates whether it is a palindrome or not. A palindrome is a word, 
      phrase, number, or other sequence of characters that reads the same forward and backward 
      (ignoring spaces, punctuation, and capitalization).
      
      >>> 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]