comefrom: <doocs>0968.Binary Tree Cameras_1.py
code: def dfs(root):
      nonlocal ans
      if root is None:
          return 2
      left, right = dfs(root.left), dfs(root.right)
      if left == 0 or right == 0:
          ans += 1
          return 1
      return 2 if left == 1 or right == 1 else 0
masked: def sample_funcname ( var_1 ) :
      nonlocal var_2
      if var_1 is None :
          return 2
      left , right = var_0 ( var_1.left ) , var_0 ( var_1.right )
      if left == 0 or right == 0 :
          var_2 += 1
          return 1
      return 2 if left == 1 or right == 1 else 0
  