comefrom: <doocs>0222.Count Complete Tree Nodes_1.py
code: def depth(root):
      res = 0
      while root:
          res += 1
          root = root.left
      return res
masked: def sample_funcname ( var_0 ) :
      var_2 = 0
      while var_0 :
          var_2 += 1
          var_0 = var_0.left
      return var_2
  