comefrom: <doocs>0863.All Nodes Distance K in Binary Tree_1.py
code: def parents(root, prev):
      nonlocal p
      if root is None:
          return
      p[root] = prev
      parents(root.left, root)
      parents(root.right, root)
masked: def sample_funcname ( var_1 , var_2 ) :
      nonlocal var_3
      if var_1 is None :
          return
      var_3 [ var_1 ] = var_2
      var_0 ( var_1.left , var_1 )
      var_0 ( var_1.right , var_1 )
  