Is it a error in aprioriGen?

[brisksea]

In chapter 11

def aprioriGen(Lk, k): #creates Ck
    retList = []
    lenLk = len(Lk)
    for i in range(lenLk):
        for j in range(i+1, lenLk): 
            L1 = list(Lk[i])[:k-2]; L2 = list(Lk[j])[:k-2]
            L1.sort(); L2.sort()
            if L1==L2: #if first k-2 elements are equal
                retList.append(Lk[i] | Lk[j]) #set union
    return retList

I think the L1 and L2 should sort first, then extract the front k-2 items to compare. Take the example:
L1 = [1,2]
L2 = {3, 1}
Though, when a set converted to a list, it's usually sorted.