def most_wanted(text: str) -> str:
    text = text.lower()
    letters = []
    max = 0
    for letter in text:
        if letter.isalpha():
            if letter not in letters:
                count = text.count(letter)
                if max == count:
                    letters.append(letter)
                if count > max:
                    letters = [letter]
                    max = count
    return letters


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