comefrom: <doocs>1022.Sum of Root To Leaf Binary Numbers_1.py
code: def dfs(root, t):
      if root is None:
          return 0
      t = (t << 1) | root.val
      if root.left is None and root.right is None:
          return t
      return dfs(root.left, t) + dfs(root.right, t)
masked: def sample_funcname ( var_1 , var_2 ) :
      if var_1 is None :
          return 0
      var_2 = ( var_2 << 1 ) | var_1.val
      if var_1.left is None and var_1.right is None :
          return var_2
      return var_0 ( var_1.left , var_2 ) + var_0 ( var_1.right , var_2 )
  