langchain/callbacks/manager.py/_ahandle_event
async def _ahandle_event(
    handlers: List[BaseCallbackHandler],
    event_name: str,
    ignore_condition_name: Optional[str],
    *args: Any,
    **kwargs: Any,
) -> None:
    """Generic event handler for AsyncCallbackManager."""
    await asyncio.gather(
        *(
            _ahandle_event_for_handler(
                handler, event_name, ignore_condition_name, *args, **kwargs
            )
            for handler in handlers
        )
    )