comefrom: <doocs>0979.Distribute Coins in Binary Tree_1.py
code: def dfs(root):
      nonlocal ans
      if root is None:
          return 0
      left, right = dfs(root.left), dfs(root.right)
      ans += abs(left) + abs(right)
      return left + right + root.val - 1
masked: def sample_funcname ( var_1 ) :
      nonlocal var_2
      if var_1 is None :
          return 0
      left , right = var_0 ( var_1.left ) , var_0 ( var_1.right )
      var_2 += abs ( left ) + abs ( right )
      return left + right + var_1.val - 1
  