Bug Report for binary-tree-diameter

[darce2]

Bug Report for https://neetcode.io/problems/binary-tree-diameter

Please describe the bug below and include any steps to reproduce the bug or screenshots if possible.

This solution returns correct but is actually incorrect. This test case proves it it is incorrect but neetcode allows the below submission as correct.
[1,2,3,4,5,null,null,6,7,8,9]

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right

class Solution:
    def diameterOfBinaryTree(self, root: Optional[TreeNode]) -> int:
        def dfs(node, count):
            if node.left and node.right:
                return dfs(node.left, 1) +  dfs(node.right, 1)

            elif node.left:
                return dfs(node.left, count + 1)

            elif node.right:
                return dfs(node.right, count + 1)

            return count

        return dfs(root, 0)