如何创建将二叉树转换为元组的函数？

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

def tree_to_tuple(root):
    if root is None:
        return None
    return (root.val, tree_to_tuple(root.left), tree_to_tuple(root.right))

# 示例用法
# 创建二叉树
root = TreeNode(1)
root.left = TreeNode(2)
root.right = TreeNode(3)
root.left.left = TreeNode(4)
root.left.right = TreeNode(5)

# 将二叉树转换为元组
result = tree_to_tuple(root)
print(result)