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# Definition for a binary tree node.# class TreeNode:#     def __init__(self, val=0, left=None, right=None):#         self.val = val#         self.left = left#         self.right = rightclass Solution:    def inorderTraversal(self, root: TreeNode) -> List[int]:        res = []        def inorder(root):            if root is None:                return            else:                inorder(root.left)                res.append(root.val)                inorder(root.right)        inorder(root)         return res

class Solution:    def postorderTraversal(self, root: TreeNode) -> List[int]:        res = []        def postorder(root):            if root is None:                return                        postorder(root.left)            postorder(root.right)            res.append(root.val)                postorder(root)        return res

class Solution:    def preorderTraversal(self, root: TreeNode) -> List[int]:        res = []        def preorder(root):            if root is None:                return             res.append(root.val)            preorder(root.left)            preorder(root.right)                preorder(root)        return res