python列表对特定元素的应用？

如图，list2里面含有（‘3’‘4’‘3’）这种元素，我就不想把它加入到list1里面，我希望把list3,list4加入到list1里面，虽然list4里面也有重复元素（‘3’‘4’‘5’‘3’）这种，但它不是aba这种情况，我就可以接受。请问该如何写代码使得li1变成list？

list1=[]


list2=['1','2','3','4','3','5']
list3=['1','2','3','4','5']
list4=['1','2','3','4','5','3','6']


li=[['1','2','3','4','3','5'],['1','2','3','4','5'],['1','2','3','4','5','3','6']]
list=[['1','2','3','4','5'],['1','2','3','4','5','3','6']]

list1 = []

list2 = ['1', '2', '3', '4', '3', '5']
list3 = ['1', '2', '3', '4', '5']
list4 = ['1', '2', '3', '4', '5', '3', '6']

li1 = [['1', '2', '3', '4', '3', '5'], ['1', '2', '3', '4', '5'], ['1', '2', '3', '4', '5', '3', '6']]
li2 = [['1', '2', '3', '4', '5'], ['1', '2', '3', '4', '5', '3', '6']]

# aba形式的列表排除
ret_list = []

for li in [list2, list3, list4]:
    for i, ele in enumerate(li[2:]):
        if ele == li[i]:
            break
    else:
        ret_list.append(li)

print(ret_list)