Python set mutations : AttributeError: 'set' object has no attribute 'k'

Question

I have to actually solve the problem in the image. But I am unable to get why it is generating attribute error. can someone please explain what it means and how it can be avoided in my code.[ problem ]

A= int(input())
set1=set(map(int,input().split()))
N=int(input())
for i in range(N):
    k,*a=input().split()
    set2=set(map(int,input().split()))
    set1.k(set2)

print(sum(set1))

Answer 1

set1.k(set2). what are you trying to do here? If you want to update or add use:

set1.add(set2)
set1.update(set2)