Not sure how to return the first letter.

Also, for the 'Aaaooo!!!!' test, it is working properly in the 'try it' section but not in the 'check and run' section.

def checkio(text):
    text = text.lower()
    mwl = {}
    for letter in text:
        if letter not in mwl:
            mwl[letter] = 1
        else:
            mwl[letter] += 1

    for letter in sorted(mwl, key = mwl.get, reverse = True):
        if letter.isalpha():
            letter = sorted(list(letter))
            return letter[0]