如何实现包含整数和空指针的双向链表？

class Node:
    def __init__(self, value):
        self.value = value
        self.prev = None
        self.next = None

class DoublyLinkedList:
    def __init__(self):
        self.head = None
        self.tail = None

def insert(self, value):
    new_node = Node(value)
    if self.head is None:
        self.head = new_node
        self.tail = new_node
    else:
        new_node.prev = self.tail
        self.tail.next = new_node
        self.tail = new_node

def delete(self, value):
    current = self.head
    while current is not None:
        if current.value == value:
            if current.prev is not None:
                current.prev.next = current.next
            else:
                self.head = current.next
            if current.next is not None:
                current.next.prev = current.prev
            else:
                self.tail = current.prev
            break
        current = current.next

def print_list(self):
    current = self.head
    while current is not None:
        print(current.value)
        current = current.next