from __future__ import annotations
from dataclasses import dataclass


@dataclass
class ListNode():
    value: str
    next : ListNode

class List():
    first_node: ListNode

    def insert(self, value) -> ListNode:
        pass

    def append(self, value) -> ListNode:
        pass

    def __str__(self):
        pass

string_list = List()
string_list.append('a')
string_list.append('b')
string_list.append('c')
string_list.append('d')
# -> List(['a','b','c','d'])
print(string_list)