I am currently stuck on Leetcode 707: Design a linked list, I think I have it mostly down but I am only passing 62/65 testcases. The problem seems to be with the deleteAtIndex function when I try to delete from index 0. I am using the 2 dummy doubly linked list approach. I thought my logic is correct, because if the index is already 0 it should skip the while loop and simply delete the first node correct? Except I tried testing it on my own and it does not work for some reason, maybe I am missing something simple? Any help would be great, thanks!

class ListNode:
    def __init__(self, val):
        self.val = val
        self.next = None
        self.prev = None

class MyLinkedList:

    def __init__(self):
        self.left = ListNode(0)
        self.right = ListNode(0)
        self.left.next = self.right
        self.right.prev = self.left

    def get(self, index: int) -> int:
        cur = self.left.next
        while index > 0 and cur != None:
            index -= 1
            cur = cur.next

        if cur != None and cur != self.right and index == 0:
            return cur.val
        else:
            return -1

    def addAtHead(self, val: int) -> None:
        new_node = ListNode(val)
        after_head = self.left.next
        after_head.prev = new_node
        new_node.next = after_head
        self.left.next = new_node
        new_node.prev = self

    def addAtTail(self, val: int) -> None:
        new_node = ListNode(val)
        before_end = self.right.prev
        before_end.next = new_node
        new_node.prev = before_end
        self.right.prev = new_node
        new_node.next = self.right

    def addAtIndex(self, index: int, val: int) -> None:
        new_node = ListNode(val)

        cur = self.left.next
        while index > 0 and cur != None:
            index -= 1
            cur = cur.next

        if cur == None:
            return
        
        if cur.val == 0 and cur.next == None:
            before_end = self.right.prev
            before_end.next = new_node
            new_node.prev = before_end
            self.right.prev = new_node
            new_node.next = self.right
        elif cur.val == 0 and cur.prev == None:
            after_head = self.left.next
            after_head.prev = new_node
            new_node.next = after_head
            self.left.next = new_node
            new_node.prev = self
        else:
            cur.prev.next = new_node
            new_node.prev = cur.prev
            cur.prev = new_node
            new_node.next = cur

    def deleteAtIndex(self, index: int) -> None:
        cur = self.left.next

        while index > 0 and cur != None:
            index -= 1
            cur = cur.next
        
        if cur != None and cur != self.right and index == 0:
            cur.prev.next = cur.next
            cur.next.prev = cur.prev