def.concat(xsbptional ListNode.hu ys: Optional[ListNode]) -> Optional[ListNode]: Return the head of a linked list that represents the concatenation of the given lists, such that xs comes before ys. >>> XS = ListNode(1, ListNode(2, ListNode(3, None))) >>> ys = ListNode(4, ListNode(5, None)) >>> concat(xs, ys) ListNode(1, ListNode(2, ListNode(3, ListNode(4, ListNode(5, None))))) a def sum_List(head: Optional ListNode1)->int: RE Return the sum of all integers in each ListNode in the list. If the list is empty, return 0. >>> head = ListNode(1, ListNode(2, ListNode(3, None))) >>> sum_List(head) 6 ANH