add example for memory (#8552)

docs/extras/guides/expression_language/cookbook.ipynb

@@ -1238,10 +1238,163 @@
     "chain.invoke({\"input\": \"whats 2 plus 2\"})"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "5062941a",
+   "metadata": {},
+   "source": [
+    "## Memory\n",
+    "\n",
+    "This shows how to add memory to an arbitrary chain. Right now, you can use the memory classes but need to hook it up manually"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 99,
+   "id": "7998efd8",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from langchain.memory import ConversationBufferMemory\n",
+    "from langchain.schema.runnable import RunnableMap\n",
+    "from langchain.prompts import MessagesPlaceholder\n",
+    "model = ChatOpenAI()\n",
+    "prompt = ChatPromptTemplate.from_messages([\n",
+    "    (\"system\", \"You are a helpful chatbot\"),\n",
+    "    MessagesPlaceholder(variable_name=\"history\"),\n",
+    "    (\"human\", \"{input}\")\n",
+    "])"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 100,
+   "id": "fa0087f3",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "memory = ConversationBufferMemory(return_messages=True)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 101,
+   "id": "06b531ae",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "{'history': []}"
+      ]
+     },
+     "execution_count": 101,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "memory.load_memory_variables({})"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 102,
+   "id": "d9437af6",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "chain = RunnableMap({\n",
+    "    \"input\": lambda x: x[\"input\"],\n",
+    "    \"memory\": memory.load_memory_variables\n",
+    "}) | {\n",
+    "    \"input\": lambda x: x[\"input\"],\n",
+    "    \"history\": lambda x: x[\"memory\"][\"history\"]\n",
+    "} | prompt | model"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 103,
+   "id": "bed1e260",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "AIMessage(content='Hello Bob! How can I assist you today?', additional_kwargs={}, example=False)"
+      ]
+     },
+     "execution_count": 103,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "inputs = {\"input\": \"hi im bob\"}\n",
+    "response = chain.invoke(inputs)\n",
+    "response"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 104,
+   "id": "890475b4",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "memory.save_context(inputs, {\"output\": response.content})"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 105,
+   "id": "e8fcb77f",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "{'history': [HumanMessage(content='hi im bob', additional_kwargs={}, example=False),\n",
+       "  AIMessage(content='Hello Bob! How can I assist you today?', additional_kwargs={}, example=False)]}"
+      ]
+     },
+     "execution_count": 105,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "memory.load_memory_variables({})"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 106,
+   "id": "d837d5c3",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "AIMessage(content='Your name is Bob. You mentioned it in your previous message. Is there anything else I can help you with, Bob?', additional_kwargs={}, example=False)"
+      ]
+     },
+     "execution_count": 106,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "inputs = {\"input\": \"whats my name\"}\n",
+    "response = chain.invoke(inputs)\n",
+    "response"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,
-   "id": "9be88499",
+   "id": "179d3c03",
    "metadata": {},
    "outputs": [],
    "source": []