input: Write a python function to check if a word is a palindrome.
  assert is_palindrome('malayalam') == True
  assert is_palindrome('rotator') == True
  assert is_palindrome('civic') == True
  assert is_palindrome('python') == False
  assert is_palindrome('racecar') == True
output: def is_palindrome(word):
      return word == word[::-1]