def insert(head: Optional[listNode], val: int, index: int) -> ListNode: Return the head of a linked list with a listNode containing val at position index in the list. If index is outside the bounds of the list (including if the initial list is empty), the new ListNode should be appended to the end. >>> head = ListNode(1, ListNode(2, ListNode(3, None))) >>> insert(head, 4, 0) ListNode(4, ListNode(1, ListNode (2, ListNode(3, None)))) def remove(head: Optional[ListNode], index: int) -> Optional[ListNode]: Return the head of a linked list with the ListNode at position index removed. If index is outside the bounds of the list, raise an IndexError. >>> head = listNode(1, ListNode(2, ListNode(3, None))) >>> remove(head, 0) ListNode (2, ListNode(3, None)) def index(head: Optional[ListNode], val: int) -> int: Return the position of the ListNode containing val. If such a node does not exist, return -1. >>> head = ListNode(1, ListNode(2, ListNode(3, None))) >>> index(head, 3) 2