如何修复单链表方法追加中的错误

class ListNode:
    def __init__(self, value=0, next=None):
        self.value = value
        self.next = next

def append_to_linked_list(head, new_value):
    new_node = ListNode(new_value)
    
    # 如果链表为空，直接返回新节点作为头节点
    if not head:
        return new_node
    
    # 遍历链表直到找到尾节点
    current = head
    while current.next:
        current = current.next
    
    # 更新尾节点的next指针，指向新节点
    current.next = new_node
    
    return head

# 测试代码
if __name__ == "__main__":
    # 创建一个简单的链表: 1 -> 2 -> None
    head = ListNode(1)
    head.next = ListNode(2)
    
    # 追加新节点值为3
    head = append_to_linked_list(head, 3)
    
    # 打印链表验证结果
    current = head
    while current:
        print(current.value, end=" -> ")
        current = current.next
    print("None")  # 输出应为: 1 -> 2 -> 3 -> None