Adding ability to return_pl_id to all PromptLayer Models in LangChain (#1699)

PromptLayer now has support for [several different tracking
features.](https://magniv.notion.site/Track-4deee1b1f7a34c1680d085f82567dab9)
In order to use any of these features you need to have a request id
associated with the request.

In this PR we add a boolean argument called `return_pl_id` which will
add `pl_request_id` to the `generation_info` dictionary associated with
a generation.

We also updated the relevant documentation.

docs/modules/chat/examples/promptlayer_chatopenai.ipynb

@@ -123,6 +123,40 @@
    "id": "05e9e2fe",
    "metadata": {},
    "source": []
+  },
+  {
+   "attachments": {},
+   "cell_type": "markdown",
+   "id": "c43803d1",
+   "metadata": {},
+   "source": [
+    "## Using PromptLayer Track\n",
+    "If you would like to use any of the [PromptLayer tracking features](https://magniv.notion.site/Track-4deee1b1f7a34c1680d085f82567dab9), you need to pass the argument `return_pl_id` when instantializing the PromptLayer LLM to get the request id.  "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "b7d4db01",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "chat = PromptLayerChatOpenAI(return_pl_id=True)\n",
+    "chat_results = chat.generate([[HumanMessage(content=\"I am a cat and I want\")]])\n",
+    "\n",
+    "for res in chat_results.generations:\n",
+    "    pl_request_id = res[0].generation_info[\"pl_request_id\"]\n",
+    "    promptlayer.track.score(request_id=pl_request_id, score=100)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "13e56507",
+   "metadata": {},
+   "source": [
+    "Using this allows you to track the performance of your model in the PromptLayer dashboard. If you are using a prompt template, you can attach a template to a request as well.\n",
+    "Overall, this gives you the opportunity to track the performance of different templates and models in the PromptLayer dashboard."
+   ]
   }
  ],
  "metadata": {
@@ -141,11 +175,11 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.8.8"
+   "version": "3.8.8 (default, Apr 13 2021, 12:59:45) \n[Clang 10.0.0 ]"
   },
   "vscode": {
    "interpreter": {
-    "hash": "c4fe2cd85a8d9e8baaec5340ce66faff1c77581a9f43e6c45e85e09b6fced008"
+    "hash": "8a5edab282632443219e051e4ade2d1d5bbc671c781051bf1437897cbdfea0f1"
    }
   }
  },