[Check-IO] The Most Wanted Letter

[1] Problem: https://py.checkio.org/en/mission/most-wanted-letter/
[2] My solutions

def checkio(text: str) -> str:

    #replace this for solution
    text = text.lower()
    word_list = list(dict.fromkeys(text))
    word_dict = {}
    for word in word_list:
        if word.isalpha(): word_dict[word] = text.count(word)
    
    return sorted(word_dict.items(),  key=(lambda x: (-x[1], x[0])))[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.")

[3] Best solution

from string import ascii_lowercase as letters
checkio = lambda text: max(letters, key=text.lower().count)