NameError: name 'self' is not defined

[walter]

But i need to add two number: one number i345 is in a linkedlist L1 and 678 the other number in another linked list L2. And also the output will be put in some nodes of another linked list. So the result of the sum wll be 1023 and i need to put 1023 in a different linked list of the class Solution.
Walter