comefrom: <doocs>1339.Maximum Product of Splitted Binary Tree_1.py
code: def dfs(root):
      nonlocal s, ans
      if root is None:
          return 0
      t = root.val + dfs(root.left) + dfs(root.right)
      if t < s:
          ans = max(ans, t * (s - t))
      return t
masked: def sample_funcname ( var_1 ) :
      nonlocal var_2 , var_3
      if var_1 is None :
          return 0
      var_9 = var_1.val + var_0 ( var_1.left ) + var_0 ( var_1.right )
      if var_9 < var_2 :
          var_3 = max ( var_3 , var_9 * ( var_2 - var_9 ) )
      return var_9
  