Load the right checkpoint for a subgraph during replay.
On the first call for a given subgraph namespace, returns the latest checkpoint created before the replay point. On subsequent calls (e.g. the same subgraph in a later loop iteration), falls back to normal latest-checkpoint loading.
get_checkpoint(
self,
checkpoint_ns: str,
checkpointer: BaseCheckpointSaver,
checkpoint_config: RunnableConfig
) -> CheckpointTuple | None