fix(serializer): add dataclass and set serialization support for langmem objects

- Add support for serializing/deserializing dataclass objects (e.g., RunningSummary)
- Add special handling for sets in nested structures
- Prevent loss of type information when dataclasses are serialized
- Fix AttributeError when langmem SummarizationNode stores context in state

Changes:
- Preprocess dataclass instances to LangChain constructor format before serialization
- Add _reconstruct_from_constructor() to rebuild objects from constructor format
- Handle sets with special __set_items__ marker to preserve contents
- Update _revive_if_needed() to detect when parent reviver returns unchanged dict

Tests:
- Add comprehensive test suite in test_langmem_serialization.py
- Test roundtrip serialization of RunningSummary objects
- Test nested dataclasses in dicts and lists
- All 382 tests passing

Fixes the error in create-react-agent-manage-message-history.ipynb where
RunningSummary objects were being deserialized as dicts instead of proper
objects, causing AttributeError: 'dict' object has no attribute 'summarized_message_ids'

Author: bsbodden

examples/create-react-agent-hitl.ipynb

@@ -53,7 +53,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 1,
    "id": "a213e11a-5c62-4ddb-a707-490d91add383",
    "metadata": {},
    "outputs": [],
@@ -64,10 +64,18 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 2,
    "id": "23a1885c-04ab-4750-aefa-105891fddf3e",
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdin",
+     "output_type": "stream",
+     "text": [
+      "OPENAI_API_KEY:  ········\n"
+     ]
+    }
+   ],
    "source": [
     "import getpass\n",
     "import os\n",
@@ -104,10 +112,27 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 3,
    "id": "7a154152-973e-4b5d-aa13-48c617744a4c",
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "0.2.0\n",
+      "17:25:17 langgraph.checkpoint.redis INFO   Redis client is a standalone client\n"
+     ]
+    },
+    {
+     "name": "stderr",
+     "output_type": "stream",
+     "text": [
+      "/tmp/ipykernel_253/104821471.py:41: LangGraphDeprecatedSinceV10: create_react_agent has been moved to `langchain.agents`. Please update your import to `from langchain.agents import create_agent`. Deprecated in LangGraph V1.0 to be removed in V2.0.\n",
+      "  graph = create_react_agent(\n"
+     ]
+    }
+   ],
    "source": [
     "# First we initialize the model we want to use.\n",
     "from langchain_openai import ChatOpenAI\n",
@@ -164,7 +189,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 4,
    "id": "16636975-5f2d-4dc7-ab8e-d0bea0830a28",
    "metadata": {},
    "outputs": [],
@@ -181,11 +206,35 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 5,
    "id": "9ffff6c3-a4f5-47c9-b51d-97caaee85cd6",
    "metadata": {},
-   "outputs": [],
-   "source": "import uuid\n\nconfig = {\"configurable\": {\"thread_id\": str(uuid.uuid4())}}\ninputs = {\"messages\": [(\"user\", \"what is the weather in SF, CA?\")]}\n\nprint_stream(graph.stream(inputs, config, stream_mode=\"values\"))"
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "================================\u001b[1m Human Message \u001b[0m=================================\n",
+      "\n",
+      "what is the weather in SF, CA?\n",
+      "17:25:18 httpx INFO   HTTP Request: POST https://api.openai.com/v1/chat/completions \"HTTP/1.1 200 OK\"\n",
+      "==================================\u001b[1m Ai Message \u001b[0m==================================\n",
+      "Tool Calls:\n",
+      "  get_weather (call_5pXxdiKNI2XosSX5Vt9sbuBv)\n",
+      " Call ID: call_5pXxdiKNI2XosSX5Vt9sbuBv\n",
+      "  Args:\n",
+      "    location: SF, CA\n"
+     ]
+    }
+   ],
+   "source": [
+    "import uuid\n",
+    "\n",
+    "config = {\"configurable\": {\"thread_id\": str(uuid.uuid4())}}\n",
+    "inputs = {\"messages\": [(\"user\", \"what is the weather in SF, CA?\")]}\n",
+    "\n",
+    "print_stream(graph.stream(inputs, config, stream_mode=\"values\"))"
+   ]
   },
   {
    "cell_type": "markdown",
@@ -197,10 +246,19 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 6,
    "id": "3decf001-7228-4ed5-8779-2b9ed98a74ea",
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "17:25:18 langgraph WARNING   Ignoring invalid packet type <class 'dict'> in pending sends\n",
+      "Next step:  ()\n"
+     ]
+    }
+   ],
    "source": [
     "snapshot = graph.get_state(config)\n",
     "print(\"Next step: \", snapshot.next)"
@@ -218,10 +276,24 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 7,
    "id": "740bbaeb",
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "17:25:18 langgraph WARNING   Ignoring invalid packet type <class 'dict'> in pending sends\n",
+      "==================================\u001b[1m Ai Message \u001b[0m==================================\n",
+      "Tool Calls:\n",
+      "  get_weather (call_5pXxdiKNI2XosSX5Vt9sbuBv)\n",
+      " Call ID: call_5pXxdiKNI2XosSX5Vt9sbuBv\n",
+      "  Args:\n",
+      "    location: SF, CA\n"
+     ]
+    }
+   ],
    "source": [
     "print_stream(graph.stream(None, config, stream_mode=\"values\"))"
    ]
@@ -238,10 +310,31 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 8,
    "id": "1c81ed9f",
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "17:25:18 langgraph WARNING   Ignoring invalid packet type <class 'dict'> in pending sends\n",
+      "17:25:18 langgraph WARNING   Ignoring invalid packet type <class 'dict'> in pending sends\n"
+     ]
+    },
+    {
+     "data": {
+      "text/plain": [
+       "{'configurable': {'thread_id': '0f79839b-117e-4aa5-901b-5c4939d92005',\n",
+       "  'checkpoint_ns': '',\n",
+       "  'checkpoint_id': '1f0c3da6-3615-6dbc-8002-bb5ce3d337c1'}}"
+      ]
+     },
+     "execution_count": 8,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "state = graph.get_state(config)\n",
     "\n",
@@ -253,10 +346,24 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 9,
    "id": "83148e08-63e8-49e5-a08b-02dc907bed1d",
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "17:25:18 langgraph WARNING   Ignoring invalid packet type <class 'dict'> in pending sends\n",
+      "==================================\u001b[1m Ai Message \u001b[0m==================================\n",
+      "Tool Calls:\n",
+      "  get_weather (call_5pXxdiKNI2XosSX5Vt9sbuBv)\n",
+      " Call ID: call_5pXxdiKNI2XosSX5Vt9sbuBv\n",
+      "  Args:\n",
+      "    location: San Francisco\n"
+     ]
+    }
+   ],
    "source": [
     "print_stream(graph.stream(None, config, stream_mode=\"values\"))"
    ]
@@ -291,4 +398,4 @@
  },
  "nbformat": 4,
  "nbformat_minor": 5
-}
+}