Fails the All letter only once check

My Main issue is that sorted isn't taking count,key=lambda letter: -letter[1], letter[0] Its saying that positional can't come after the keyword argument but I thought -letter[1] jsut reverses and the second one was supposed to be its index?

def checkio(text: str) -> str:

#replace this for solution
text = text.lower()
count = []
for letter in list(text):
        if letter.isalpha():
            count.append((letter,text.count(letter)))
most = sorted(count, key=lambda letter: -letter[1],letter[0])
return most[0][0]

if name == 'main': print("Example:") print(checkio("Hello World!"))

#These "asserts" using only for self-checking and not necessary for auto-testing
assert checkio("Hello World!") == "l", "Hello test"
assert checkio("How do you do?") == "o", "O is most wanted"
assert checkio("One") == "e", "All letter only once."
assert checkio("Oops!") == "o", "Don't forget about lower case."
assert checkio("AAaooo!!!!") == "a", "Only letters."
assert checkio("abe") == "a", "The First."
print("Start the long test")
assert checkio("a" * 9000 + "b" * 1000) == "a", "Long."
print("The local tests are done.")