我正在学习用Python实现的链表：
$ cat linked_stack.py
class LinkedStack:
"""LIFO Stack implementation using a singly linked list for storage"""
#-------------nested Node class ------------------------------------
class _Node:
"""Lightweight, nonpublic class for storing a singly linked node."""
__slots__ = "_element", "_next"
def __init__(self, element, next): #initialize node's fields
self._element = element
self._next = next
#--------------stack methods---------------------------------------
def __init__(self):
"""Create an empty stack"""
self._head = None
self._size = 0
def top(self):
"""Return (but do not remove) the element at the top of the stack.
Raise Empty exception if the stack is empty."""
if self.is_empty():
raise Exception("Stack is empty")
return self._head._element
def __len__(self)->int:
return self._size
def is_empty(self)->bool:
return len(self._size) == 0
def push(self, e) -> None:
self._head = self._Node(e, self._head) #create and link a new node
self._size += 1
def pop(self)
对顶级方法的引用是：
def top(self):
"""Return (but do not remove) the element at the top of the stack.
Raise Empty exception if the stack is empty."""
if self.is_empty():
raise Exception("Stack is empty")
return self._head._element
我想将其注释为：
def top(self)-> _Node._element:
如何以体面的方式完成它？