[fix bug] chapter7 my_simple_agent.py 补充import类

code/chapter7/my_simple_agent.py

@@ -1,6 +1,6 @@
 # my_simple_agent.py
 from typing import Optional, Iterator
-from hello_agents import SimpleAgent, HelloAgentsLLM, Config, Message
+from hello_agents import SimpleAgent, HelloAgentsLLM, Config, Message, ToolRegistry
 import re
 
 class MySimpleAgent(SimpleAgent):

docs/chapter7/Chapter7-Building-Your-Agent-Framework.md

@@ -617,7 +617,7 @@ SimpleAgent is the most basic Agent implementation, demonstrating how to build a
 ```python
 # my_simple_agent.py
 from typing import Optional, Iterator
-from hello_agents import SimpleAgent, HelloAgentsLLM, Config, Message
+from hello_agents import SimpleAgent, HelloAgentsLLM, Config, Message, ToolRegistry
 
 class MySimpleAgent(SimpleAgent):
     """

docs/chapter7/第七章 构建你的Agent框架.md

@@ -617,7 +617,7 @@ SimpleAgent是最基础的Agent实现，它展示了如何在框架基础上构
 ```python
 # my_simple_agent.py
 from typing import Optional, Iterator
-from hello_agents import SimpleAgent, HelloAgentsLLM, Config, Message
+from hello_agents import SimpleAgent, HelloAgentsLLM, Config, Message, ToolRegistry
 
 class MySimpleAgent(SimpleAgent):
     """