input: Write a function to determine if a given string is a palindrome. The function should ignore case sensitivity. If the string is a palindrome, return True; otherwise, return False. If the string is empty, return True.
  def is_palindrome(s):
      s = s.lower()
      left = 0
      right = len(s) - 1
      
      while left < right:
          if s[left] != s[right]:
              return False
          left += 1
          right -= 1
      return True
  
  assert is_palindrome("racecar")==True
  assert is_palindrome("Racecar")==True
  assert is_palindrome("hello")==False
  assert is_palindrome("AmanaplanacanalPanama")==True
  assert is_palindrome("")==True
output: def is_palindrome(s):
      s = s.lower()
      left = 0
      right = len(s) - 1
      
      while left < right:
          if s[left] != s[right]:
              return False
          left += 1
          right -= 1
      return True