전화번호부(python)

def solution(phone_book):
    answer = True
    for i,phone in enumerate(phone_book):
        phone_book[i] = phone.replace(" ","")
    
    phone_book.sort()
    for i in range(len(phone_book)-1):
        for j in range(i+1,len(phone_book)):
            if(phone_book[j].startswith(phone_book[i])):
                answer = False
                return answer
                
    return answer