def deepestLeavesSum(self, root: Optional[TreeNode]) -> int:
    from collections import deque
    dept = 1
    tree = {}
    queue = deque()
    queue.append((dept, root))

    while queue:
        current = queue.popleft()
        dept = current[0]
        root = current[1]

        try:
            tree[dept].append(root.val)
        except:
            tree[dept] = [root.val]

        if root.left != None:
            queue.append((dept+1, root.left))
        if root.right != None:
            queue.append((dept+1, root.right))

    return sum(tree[max(tree)])