parent_run_id: Optional[UUID] = None,
        **kwargs: Any,
    ) -> AsyncCallbackManagerForToolRun:
        """Run when tool starts running.
        Args:
            serialized (Dict[str, Any]): The serialized tool.
            input_str (str): The input to the tool.
            run_id (UUID, optional): The ID of the run. Defaults to None.
            parent_run_id (UUID, optional): The ID of the parent run.
                Defaults to None.
        Returns:
            AsyncCallbackManagerForToolRun: The async callback manager
                for the tool run.
        """
        if run_id is None:
            run_id = uuid.uuid4()
        await _ahandle_event(
            self.handlers,
            "on_tool_start",
            "ignore_agent",
            serialized,
            input_str,
            run_id=run_id,
            parent_run_id=self.parent_run_id,
            tags=self.tags,
            metadata=self.metadata,
            **kwargs,
        )
        return AsyncCallbackManagerForToolRun(
            run_id=run_id,
            handlers=self.handlers,
            inheritable_handlers=self.inheritable_handlers,
            parent_run_id=self.parent_run_id,
            tags=self.tags,
            inheritable_tags=self.inheritable_tags,
            metadata=self.metadata,
            inheritable_metadata=self.inheritable_metadata,
        )
[docs]    async def on_retriever_start(
        self,
        serialized: Dict[str, Any],
        query: str,
        run_id: Optional[UUID] = None,
        parent_run_id: Optional[UUID] = None,
        **kwargs: Any,
    ) -> AsyncCallbackManagerForRetrieverRun:
        """Run when retriever starts running."""