build

en/docs/chapter_stack_and_queue/queue.md

@@ -368,7 +368,7 @@ Below is the code for implementing a queue using a linked list:
 
         def is_empty(self) -> bool:
             """判断队列是否为空"""
-            return not self._front
+            return self._size == 0
 
         def push(self, num: int):
             """入队"""