docs(reference): filter class methods and add missing docstrings (#4463)

libs/checkpoint-postgres/langgraph/checkpoint/postgres/__init__.py

@@ -27,6 +27,8 @@ Conn = _internal.Conn  # For backward compatibility
 
 
 class PostgresSaver(BasePostgresSaver):
+    """Checkpointer that stores checkpoints in a Postgres database."""
+
     lock: threading.Lock
 
     def __init__(

libs/checkpoint-postgres/langgraph/checkpoint/postgres/aio.py

@@ -27,6 +27,8 @@ Conn = _ainternal.Conn  # For backward compatibility
 
 
 class AsyncPostgresSaver(BasePostgresSaver):
+    """Asynchronous checkpointer that stores checkpoints in a Postgres database."""
+
     lock: asyncio.Lock
 
     def __init__(