input: Write a function to determine if a given string `s` is a palindrome. If `s` is a palindrome, the function should return True; otherwise, it should return False. A string is a palindrome if it reads the same backward as forward.
  
  assert is_palindrome("madam")==True
  assert is_palindrome("racecar")==True
  assert is_palindrome("hello")==False
  assert is_palindrome("")==True
  assert is_palindrome("a")==True
output: def is_palindrome(s):
      return s == s[::-1]