input: 
  def is_palindrome(s):
      """Check if the given string is a palindrome.
      >>> is_palindrome("racecar")
      True
      >>> is_palindrome("hello")
      False
      """
      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
   
  
  Consider implementing the `is_palindrome` function so that it checks whether a given string reads the same forwards and backwards, returning `True` if it does and `False` otherwise. The function should be case-insensitive and should return `True` for strings like "racecar" and `False` for strings like "hello".
output:     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