input: Write a function that takes a string and checks if it is a palindrome. A palindrome is a word, phrase, number, or other sequence of characters that reads the same forward and backward. The function should return True if the string is a palindrome, otherwise False.
  
  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("deified") == True
  assert is_palindrome("Hello") == False
  assert is_palindrome("A man a plan a canal Panama") == True
  assert is_palindrome("") == True
output: def is_palindrome(s):
      s = s.lower().replace(" ", "")
      return s == s[::-1]