Serializer that uses ormsgpack, with optional fallbacks.
Security note: This serializer is intended for use within the BaseCheckpointSaver
class and called within the Pregel loop. It should not be used on untrusted
python objects. If an attacker can write directly to your checkpoint database,
they may be able to trigger code execution when data is deserialized.
Set the environment variable LANGGRAPH_STRICT_MSGPACK=true to restrict
deserialization to a built-in allowlist of safe types. You can also pass
an explicit allowed_msgpack_modules to the constructor.
