Value error:list.remove(x) :x not in list

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Python

I am trying to learn Karger's algorithm. When i was browsing, I found a code for it and I thought I would try it out. When I try to run it, however, I get an error saying the following:

Value error: list.remove(x) :x not in list at G[x].remove[v2].

def choose_random_key(G):
    v1 = random.choice(list(G.keys()))
    v2 = random.choice(list(G[v1]))
    return v1, v2

def karger(G):
    length = []
    while len(G) > 2:
        v1, v2 = choose_random_key(G)
        G[v1].extend(G[v2])
        for x in G[v2]:
            G[x].remove(v2)
            G[x].append(v1) 
        while v1 in G[v1]:
            G[v1].remove(v1)
        del G[v2]
    for key in G.keys():
        length.append(len(G[key]))
    return length[0]

def operation(n):
    i = 0
    count = 10000   
    while i < n:
        data = copy.deepcopy(G)
        min_cut = karger(data)
        if min_cut < count:
            count = min_cut
        i = i + 1
    return count


print(operation(100))

G={0: [], 1: [10, 14], 2: [5, 10], 3: [10], 4: [], 5: [4, 9, 12, 14], 6: [7, 8, 13
], 7: [1], 8: [1, 2, 4], 9: [1, 17, 18], 10: [7, 13, 19], 11: [1, 14, 16], 12: [
0, 2, 8], 13: [], 14: [], 15: [2], 16: [9, 12], 17: [2, 12, 19], 18: [0, 6, 9, 1
4], 19: [3, 16]}{0: [], 1: [10, 14], 2: [5, 10], 3: [10], 4: [], 5: [4, 9, 12, 14], 6: [7, 8, 13
], 7: [1], 8: [1, 2, 4], 9: [1, 17, 18], 10: [7, 13, 19], 11: [1, 14, 16], 12: [
0, 2, 8], 13: [], 14: [], 15: [2], 16: [9, 12], 17: [2, 12, 19], 18: [0, 6, 9, 1
4], 19: [3, 16]}

What am i doing wrong? Any help would be appreciated.