docs: Updated Together integration docs (#21388)

**Description:** Updated the together integration docs by leading with
the streaming example, explicitly specifying a model to show users how
to do that, and updating the sections to more closely match other
integrations.

docs/docs/integrations/llms/together.ipynb

@@ -7,20 +7,18 @@
    "source": [
     "# Together AI\n",
     "\n",
-    "> The Together API makes it easy to query and fine-tune leading open-source models with a couple lines of code. We have integrated the world’s leading open-source models, including Llama-3, Mixtral, DBRX, Stable Diffusion XL, and more. Read more: https://together.ai\n",
+    "[Together AI](https://www.together.ai/) offers an API to query [50+ leading open-source models](https://docs.together.ai/docs/inference-models) in a couple lines of code.\n",
     "\n",
-    "To use, you'll need an API key which you can find here:\n",
-    "https://api.together.ai/settings/api-keys. This can be passed in as init param\n",
-    "``together_api_key`` or set as environment variable ``TOGETHER_API_KEY``.\n",
-    "\n",
-    "Together API reference: https://docs.together.ai"
+    "This example goes over how to use LangChain to interact with Together AI models."
    ]
   },
   {
    "cell_type": "markdown",
    "id": "1c47fc36",
    "metadata": {},
-   "source": []
+   "source": [
+    "## Installation"
+   ]
   },
   {
    "cell_type": "code",
@@ -29,7 +27,27 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "%pip install --upgrade --quiet langchain-together"
+    "%pip install --upgrade langchain-together"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "89883202",
+   "metadata": {},
+   "source": [
+    "## Environment\n",
+    "\n",
+    "To use Together AI, you'll need an API key which you can find here:\n",
+    "https://api.together.ai/settings/api-keys. This can be passed in as an init param\n",
+    "``together_api_key`` or set as environment variable ``TOGETHER_API_KEY``.\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "8304b4d9",
+   "metadata": {},
+   "source": [
+    "## Example"
    ]
   },
   {
@@ -39,19 +57,22 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "# Running chat completions with Together AI\n",
+    "# Querying chat models with Together AI\n",
     "\n",
-    "from langchain_core.prompts import ChatPromptTemplate\n",
     "from langchain_together import ChatTogether\n",
     "\n",
-    "chat = ChatTogether()\n",
+    "# choose from our 50+ models here: https://docs.together.ai/docs/inference-models\n",
+    "chat = ChatTogether(\n",
+    "    # together_api_key=\"YOUR_API_KEY\",\n",
+    "    model=\"meta-llama/Llama-3-70b-chat-hf\",\n",
+    ")\n",
     "\n",
-    "# using chat invoke\n",
-    "chat.invoke(\"Tell me fun things to do in NYC\")\n",
-    "\n",
-    "# using chat stream\n",
+    "# stream the response back from the model\n",
     "for m in chat.stream(\"Tell me fun things to do in NYC\"):\n",
-    "    print(m)"
+    "    print(m.content, end=\"\", flush=True)\n",
+    "\n",
+    "# if you don't want to do streaming, you can use the invoke method\n",
+    "# chat.invoke(\"Tell me fun things to do in NYC\")"
    ]
   },
   {
@@ -61,7 +82,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "# Running completions with Together AI\n",
+    "# Querying code and language models with Together AI\n",
     "\n",
     "from langchain_together import Together\n",
     "\n",