minor fix up react_agent (#123)

# What does this PR do?

- address comments in
#121


## Test Plan

- see llamastack/llama-stack-apps#166

## Sources

Please link relevant resources if necessary.


## Before submitting

- [ ] This PR fixes a typo or improves the docs (you can dismiss the
other checks if that's the case).
- [ ] Ran pre-commit to handle lint / formatting issues.
- [ ] Read the [contributor
guideline](https://github.com/meta-llama/llama-stack/blob/main/CONTRIBUTING.md),
      Pull Request section?
- [ ] Updated relevant documentation.
- [ ] Wrote necessary unit or integration tests.

Author: yanxi0830

src/llama_stack_client/lib/agents/agent.py

@@ -60,8 +60,7 @@ def _process_chunk(self, chunk: AgentTurnResponseStreamChunk) -> None:
         message = chunk.event.payload.turn.output_message
 
         if self.output_parser:
-            parsed_message = self.output_parser.parse(message)
-            message = parsed_message
+            self.output_parser.parse(message)
 
     def _has_tool_call(self, chunk: AgentTurnResponseStreamChunk) -> bool:
         if chunk.event.payload.event_type != "turn_complete":

src/llama_stack_client/lib/agents/output_parser.py

@@ -39,10 +39,10 @@ def parse(self, output_message: CompletionMessage) -> CompletionMessage:
             Args:
                 output_message (CompletionMessage): The response message from agent turn
 
-            Returns:
-                CompletionMessage: The processed/transformed response message
+            Returns: None
+                Modifies the output_message in place
     """
 
     @abstractmethod
-    def parse(self, output_message: CompletionMessage) -> CompletionMessage:
+    def parse(self, output_message: CompletionMessage) -> None:
         raise NotImplementedError

src/llama_stack_client/lib/agents/react/output_parser.py

@@ -25,16 +25,16 @@ class ReActOutput(BaseModel):
 
 
 class ReActOutputParser(OutputParser):
-    def parse(self, output_message: CompletionMessage) -> CompletionMessage:
+    def parse(self, output_message: CompletionMessage) -> None:
         response_text = str(output_message.content)
         try:
             react_output = ReActOutput.model_validate_json(response_text)
         except ValidationError as e:
             print(f"Error parsing action: {e}")
-            return output_message
+            return
 
         if react_output.answer:
-            return output_message
+            return
 
         if react_output.action:
             tool_name = react_output.action.tool_name
@@ -43,4 +43,4 @@ def parse(self, output_message: CompletionMessage) -> CompletionMessage:
                 call_id = str(uuid.uuid4())
                 output_message.tool_calls = [ToolCall(call_id=call_id, tool_name=tool_name, arguments=tool_params)]
 
-        return output_message
+        return