如何在python中实现状态空间树(二叉树)？

class Node:
    def __init__(self, value):
        self.value = value
        self.left = None
        self.right = None

class Tree:
    def __init__(self):
        self.root = None

    def insert(self, value):
        if self.root is None:
            self.root = Node(value)
        else:
            self._insert_recursive(value, self.root)

    def _insert_recursive(self, value, node):
        if value < node.value:
            if node.left is None:
                node.left = Node(value)
            else:
                self._insert_recursive(value, node.left)
        else:
            if node.right is None:
                node.right = Node(value)
            else:
                self._insert_recursive(value, node.right)

    def search(self, value):
        return self._search_recursive(value, self.root)

    def _search_recursive(self, value, node):
        if node is None or node.value == value:
            return node
        if value < node.value:
            return self._search_recursive(value, node.left)
        return self._search_recursive(value, node.right)

    def delete(self, value):
        self.root = self._delete_recursive(value, self.root)

    def _delete_recursive(self, value, node):
        if node is None:
            return node
        if value < node.value:
            node.left = self._delete_recursive(value, node.left)
        elif value > node.value:
            node.right = self._delete_recursive(value, node.right)
        else:
            if node.left is None:
                return node.right
            elif node.right is None:
                return node.left
            min_value = self._find_min_value(node.right)
            node.value = min_value
            node.right = self._delete_recursive(min_value, node.right)
        return node

    def _find_min_value(self, node):
        min_value = node.value
        while node.left is not None:
            min_value = node.left.value
            node = node.left
        return min_value

tree = Tree()
tree.insert(5)
tree.insert(3)
tree.insert(7)
tree.insert(2)
tree.insert(4)
tree.insert(6)
tree.insert(8)

print(tree.search(4))  # 输出: <__main__.Node object at 0x7f8e2c1b7f10>
tree.delete(4)
print(tree.search(4))  # 输出: None