langchain/callbacks/manager.py/BaseRunManager/__init__
class BaseRunManager:    def __init__(
        self,
        run_id: UUID,
        handlers: List[BaseCallbackHandler],
        inheritable_handlers: List[BaseCallbackHandler],
        parent_run_id: Optional[UUID] = None,
    ) -> None:
        """Initialize run manager."""
        self.run_id = run_id
        self.handlers = handlers
        self.inheritable_handlers = inheritable_handlers
        self.parent_run_id = parent_run_id