Python3 achieve flip binary tree problem

# 二叉树的结构如下
class TreeNode:
	def __init__(self, x):
		self.val = x
		self.left = None
		self.right = None

# 解决方案
class Solution:
	# 从根节点开始递归翻转其左子树和右子树
    def invertTree(self, root: TreeNode) -> TreeNode:
        if root != None:
            temp = root.right
            root.right = self.invertTree(root.left)
            root.left = self.invertTree(temp)
        return root