Fill in the code to complete the following function for checking whether a string is a palindrome.

def isPalindrome$($s$)$:

return isPalindromeHelper$($s$,0,$ len$($s$)-1)$

def isPalindromeHelper$($s$,$ low, high$)$:

if high low: # Base case

return True

elif low $]s[$high$]$: # Base case

return False

else:

return