如何在python中合并两个不相等的嵌套表？

def merge_lists(list1, list2):
    if isinstance(list1, list) and isinstance(list2, list):
        result = list1.copy()
        for item in list2:
            if item not in result:
                result.append(item)
        return result
    else:
        return "Input is not a list."

# 示例用法
nested_list1 = [[1, 2], [3, 4]]
nested_list2 = [[3, 4], [5, 6]]
merged_list = []

for sublist in nested_list1:
    merged_list = merge_lists(merged_list, sublist)

for sublist in nested_list2:
    merged_list = merge_lists(merged_list, sublist)

print(merged_list)