comefrom: <doocs>1120.Maximum Average Subtree_1.py
code: def dfs(root):
      if root is None:
          return 0, 0
      ls, ln = dfs(root.left)
      rs, rn = dfs(root.right)
      s = ls + root.val + rs
      n = ln + 1 + rn
      nonlocal ans
      ans = max(ans, s / n)
      return s, n
masked: def sample_funcname ( var_1 ) :
      if var_1 is None :
          return 0 , 0
      var_4 , var_6 = var_0 ( var_1.left )
      var_7 , var_9 = var_0 ( var_1.right )
      var_11 = var_4 + var_1.val + var_7
      var_13 = var_6 + 1 + var_9
      nonlocal var_14
      var_14 = max ( var_14 , var_11 / var_13 )
      return var_11 , var_13
  