input: Write a function to check if a string is a palindrome.
  assert is_palindrome("racecar") == True
  assert is_palindrome("hello") == False
  assert is_palindrome("madam") == True
  assert is_palindrome("step on no pets") == True
  assert is_palindrome("python") == False
output: def is_palindrome(s):
      s = s.replace(" ", "")  # Remove spaces
      return s == s[::-1]