input: Write a function to determine if a given string is a palindrome. If the string is a palindrome, the function should return True; otherwise, it should return False. If the string is empty, the function should return True.
  def is_palindrome(s):
      '''This function returns True if the string s is a palindrome and False if it isn't.''' 
      return s == s[::-1]  # Checks if s is the same as its reverse.
  assert is_palindrome('racecar')==True
  assert is_palindrome('hello')==False
  assert is_palindrome('')==True
  assert is_palindrome('a')==True
  assert is_palindrome('ab')==False
output: def is_palindrome(s):
      return s == s[::-1]