new_contents: # -*- coding:utf-8 -*-
  # Definition for a  binary tree node
  # class TreeNode:
  #     def __init__(self, x):
  #         self.val = x
  #         self.left = None
  #         self.right = None
  
  
  class Solution:
      # @param root, a tree node
      # @return a list of integers
      def inorderTraversal(self, root):
          ret = []
          if root:
              self.traversal(root, ret)
          return ret
  
      def traversal(self, root, ret):
          if root is None:
              return
          self.traversal(root.left, ret)
          ret.append(root.val)
          self.traversal(root.right, ret)
  
subject: add leetcode Binary Tree Inorder Traversal