input: Write a function to check if a given string `s` is a palindrome. A palindrome is defined as a string that reads the same forward and backward. If the string is a palindrome, the function should return True; otherwise, it should return False.
  
  def is_palindrome(s):
      '''Write your code here.'''
  
  assert is_palindrome("racecar")==True
  assert is_palindrome("noon")==True
  assert is_palindrome("python")==False
  assert is_palindrome("")==True
output: def is_palindrome(s):
      return s == s[::-1]