첫번째 시도 코드

def solution(phone_book):
    answer = True

    phone_book.sort(key=len)
    phone_book.sort(reverse=True)

    while len(phone_book) > 0:
        standard = phone_book.pop()

        phone_book_join = ' '.join(phone_book)
        if standard in phone_book_join:
            answer = False
            break

    return answer