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