docs: add python subscribe demo

docs-cn/04-develop/06-subscribe.mdx

@@ -160,7 +160,7 @@ make
 ./subscribe -sql='select * from meters where current > 10;'
 ```
 
-示例程序启动后，打开另一个终端窗口，启动 TDengine 的 shell 向 **D1001** 插入一条电流为 12A 的数据：
+示例程序启动后，打开另一个终端窗口，启动 TDengine CLI 向 **D1001** 插入一条电流为 12A 的数据：
 
 ```sql
 $ taos
@@ -172,7 +172,7 @@ $ taos
 
 ## 示例程序
 
-下面以一个示例程序介绍其具体使用方法。示例程序的目的是订阅数据库中所有电流超过 10A 的记录。
+下面的示例程序展示是如何使用连接器订阅所有电流超过 10A 的记录。
 
 ### 准备数据
 
@@ -206,16 +206,16 @@ Query OK, 5 row(s) in set (0.004896s)
   <TabItem label="Java" value="java">
       <Java/>
   </TabItem>
-  {/* <TabItem label="Python" value="Python">
+  <TabItem label="Python" value="Python">
       <Python/>
   </TabItem>
-  <TabItem label="Go" value="go">
+  {/* <TabItem label="Go" value="go">
       <Go/>
-  </TabItem>
+  </TabItem> */}
   <TabItem label="Rust" value="rust">
       <Rust/>
   </TabItem>
-  <TabItem label="Node.js" value="nodejs">
+  {/* <TabItem label="Node.js" value="nodejs">
       <Node/>
   </TabItem>
   <TabItem label="C#" value="csharp">
@@ -238,7 +238,7 @@ ts: 1597464600000	current: 10.3	voltage: 220	phase: 1	location: Beijing.Haidian
 ts: 1597465200000	current: 11.2	voltage: 220	phase: 1	location: Beijing.Haidian	groupid : 2
 ```
 
-接着，使用 taos 客户端向表中新增一条数据：
+接着，使用 TDengine CLI 向表中新增一条数据：
 
 ```
 # taos

docs-examples/python/handle_exception.py

 import taos
 
-conn: taos.TaosConnection = None
 try:
     conn = taos.connect()
     conn.execute("CREATE TABLE 123")  # wrong sql
@@ -12,9 +11,6 @@ except taos.Error as e:
 except BaseException as other:
     print("exception occur")
     print(other)
-finally:
-    if conn is not None:
-        conn.close()
 
 # output:
 # [0x0216]: syntax error near 'Incomplete SQL statement'

docs-examples/python/subscribe_demo.py

-import taos
\ No newline at end of file
+"""
+Python asynchronous subscribe demo.
+run on Linux system with: python3 subscribe_demo.py
+"""
+
+from ctypes import c_void_p
+
+import taos
+import time
+
+
+def query_callback(p_sub, p_result, p_param, code):
+    """
+    :param p_sub: pointer returned by native API -- taos_subscribe
+    :param p_result: pointer to native TAOS_RES
+    :param p_param: None
+    :param code: error code
+    :return: None
+    """
+    print("in callback")
+    result = taos.TaosResult(c_void_p(p_result))
+    # raise exception if error occur
+    result.check_error(code)
+    for row in result.rows_iter():
+        print(row)
+    print(f"{result.row_count} rows consumed.")
+
+
+if __name__ == '__main__':
+    conn = taos.connect()
+    restart = True
+    topic = "topic-meter-current-bg"
+    sql = "select * from power.meters where current > 10"  # Error sql
+    interval = 2000  # consumption interval in microseconds.
+    _ = conn.subscribe(restart, topic, sql, interval, query_callback)
+    # Note: we received the return value as _ above, to avoid the TaosSubscription object to be deleted by gc.
+    while True:
+        time.sleep(10)  # use Ctrl + C to interrupt