Add typing annotations to Python codes. (#411)

docs/chapter_stack_and_queue/deque.md

@@ -83,7 +83,7 @@
 
     ```python title="deque.py"
     """ 初始化双向队列 """
-    deque = deque()
+    deque: Deque[int] = collections.deque()
     
     """ 元素入队 """
     deque.append(2)      # 添加至队尾
@@ -93,18 +93,18 @@
     deque.appendleft(1)
     
     """ 访问元素 """
-    front = deque[0]  # 队首元素
-    rear = deque[-1]  # 队尾元素
+    front: int = deque[0]  # 队首元素
+    rear: int = deque[-1]  # 队尾元素
     
     """ 元素出队 """
-    pop_front = deque.popleft()  # 队首元素出队
-    pop_rear = deque.pop()       # 队尾元素出队
+    pop_front: int = deque.popleft()  # 队首元素出队
+    pop_rear: int = deque.pop()       # 队尾元素出队
     
     """ 获取双向队列的长度 """
-    size = len(deque)
+    size: int = len(deque)
     
     """ 判断双向队列是否为空 """
-    is_empty = len(deque) == 0
+    is_empty: bool = len(deque) == 0
     ```
 
 === "Go"