swapcase

• It converts all uppercase characters to lowercase and vice versa.

def makeGood(s):
    stack=[]
    for i in s:
        if stack and stack[-1]!=i and stack[-1].lower()==i.lower():
            stack.pop()
        else:
            stack.append(i)
    return ''.join(stack)

s='leEeetcode'
makeGood(s)

>>>

'leetcode'

### IS SAME AS BELOW

def makeGood(s):
    stack=[]
    for i in s:
        if stack and stack[-1]==i.swapcase():
            stack.pop()
        else:
            stack.append(i)
    return ''.join(stack)

s='leEeetcode'
makeGood(s)