def on_event_start(
        self,
        event_type: CBEventType,
        payload: Optional[Dict[str, Any]] = None,
        event_id: str = "",
        parent_id: str = "",
        **kwargs: Any,
    ) -> str:
        """
        Args:
            event_type (CBEventType): event type to store.
            payload (Optional[Dict[str, Any]]): payload to store.
            event_id (str): event id to store.
            parent_id (str): parent event id.

        """
        return ""

        Args:
            event_type (CBEventType): event type to store.
            payload (Optional[Dict[str, Any]]): payload to store.
            event_id (str): event id to store.
            parent_id (str): parent event id.

        
llama-index-integrations/callbacks/llama-index-callbacks-aim/llama_index/callbacks/aim/base.py