human
I found an interesting problem on https://leetcode.com/problems/maximum-level-sum-of-a-binary-tree/:
Given the root of a binary tree, the level of its root is 1, the level of its children is 2, and so on.
Return the smallest level X such that the sum of all the values of nodes at level X is maximal.
 
Example 1:

Input: root = [1,7,0,7,-8,null,null]
Output: 2
Explanation: 
Level 1 sum = 1.
Level 2 sum = 7 + 0 = 7.
Level 3 sum = 7 + -8 = -1.
So we return the level with the maximum sum which is level 2.

Example 2:
Input: root = [989,null,10250,98693,-89388,null,null,null,-32127]
Output: 2

 
Constraints:

The number of nodes in the tree is in the range [1, 104].
-105 <= Node.val <= 105

I tried it in Python, but could not do it. Can you solve it?
assistant
#Here is the Python program you requested.

# 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 maxLevelSum(self, root: TreeNode) -> int:
        self.max_sum = {}
        
        def sum_tree(node: TreeNode,level):
            
            if not node:
                return
            sum_tree(node.left,level+1)
            sum_tree(node.right,level+1)
            if level in self.max_sum:
                self.max_sum[level] +=  node.val
            else:
                self.max_sum[level] =  node.val
            
        sum_tree(root,1)
        output, max_val = float('inf'), -float('inf')
        for key, val in list(self.max_sum.items()):
            if val > max_val:
                output, max_val = key, val
            elif val == max_val:
                output = min(key, output)
        return output