docs: Update a note about how to track azure openai's token usage when streaming (#30409)

- **Description:** Update a note about how to track azure openai's token
usage when streaming
  - **Issue:** #30390 
  - **Dependencies:** None
  - **Twitter handle:** None

---------

Co-authored-by: Chester Curme <chester.curme@gmail.com>

docs/docs/how_to/chat_token_usage_tracking.ipynb

@@ -29,6 +29,31 @@
     "%pip install -qU langchain-anthropic langchain-openai"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "c71b676a",
+   "metadata": {},
+   "source": [
+    ":::note A note on streaming with OpenAI\n",
+    "\n",
+    "OpenAI's Chat Completions API does not stream token usage statistics by default (see API reference\n",
+    "[here](https://platform.openai.com/docs/api-reference/completions/create#completions-create-stream_options)).\n",
+    "To recover token counts when streaming with `ChatOpenAI`, set `stream_usage=True` as\n",
+    "demonstrated in this guide.\n",
+    "\n",
+    "For `AzureChatOpenAI`, set `stream_options={\"include_usage\": True}` when calling\n",
+    "`.(a)stream`, or initialize with:\n",
+    "\n",
+    "```python\n",
+    "AzureChatOpenAI(\n",
+    "    ...,\n",
+    "    model_kwargs={\"stream_options\": {\"include_usage\": True}},\n",
+    ")\n",
+    "```\n",
+    "\n",
+    ":::"
+   ]
+  },
   {
    "cell_type": "markdown",
    "id": "598ae1e2-a52d-4459-81fd-cdc68b06742a",