community[minor]: Adds Llamafile as an LLM (#17431)

* **Description:** Adds a simple LLM implementation for interacting with
[llamafile](https://github.com/Mozilla-Ocho/llamafile)-based models.
* **Dependencies:** N/A
* **Issue:** N/A

**Detail**
[llamafile](https://github.com/Mozilla-Ocho/llamafile) lets you run LLMs
locally from a single file on most computers without installing any
dependencies.

To use the llamafile LLM implementation, the user needs to:

1. Download a llamafile e.g.
https://huggingface.co/jartine/TinyLlama-1.1B-Chat-v1.0-GGUF/resolve/main/TinyLlama-1.1B-Chat-v1.0.Q5_K_M.llamafile?download=true
2. Make the file executable.
3. Run the llamafile in 'server mode'. (All llamafiles come packaged
with a lightweight server; by default, the server listens at
`http://localhost:8080`.)


```bash
wget https://url/of/model.llamafile
chmod +x model.llamafile
./model.llamafile --server --nobrowser
```

Now, the user can invoke the LLM via the LangChain client:

```python
from langchain_community.llms.llamafile import Llamafile

llm = Llamafile()

llm.invoke("Tell me a joke.")
```

docs/docs/integrations/llms/llamafile.ipynb

@@ -0,0 +1,133 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Llamafile\n",
+    "\n",
+    "[Llamafile](https://github.com/Mozilla-Ocho/llamafile) lets you distribute and run LLMs with a single file.\n",
+    "\n",
+    "Llamafile does this by combining [llama.cpp](https://github.com/ggerganov/llama.cpp) with [Cosmopolitan Libc](https://github.com/jart/cosmopolitan) into one framework that collapses all the complexity of LLMs down to a single-file executable (called a \"llamafile\") that runs locally on most computers, with no installation.\n",
+    "\n",
+    "## Setup\n",
+    "\n",
+    "1. Download a llamafile for the model you'd like to use. You can find many models in llamafile format on [HuggingFace](https://huggingface.co/models?other=llamafile). In this guide, we will download a small one, `TinyLlama-1.1B-Chat-v1.0.Q5_K_M`. Note: if you don't have `wget`, you can just download the model via this [link](https://huggingface.co/jartine/TinyLlama-1.1B-Chat-v1.0-GGUF/resolve/main/TinyLlama-1.1B-Chat-v1.0.Q5_K_M.llamafile?download=true).\n",
+    "\n",
+    "```bash\n",
+    "wget https://huggingface.co/jartine/TinyLlama-1.1B-Chat-v1.0-GGUF/resolve/main/TinyLlama-1.1B-Chat-v1.0.Q5_K_M.llamafile\n",
+    "```\n",
+    "\n",
+    "2. Make the llamafile executable. First, if you haven't done so already, open a terminal. **If you're using MacOS, Linux, or BSD,** you'll need to grant permission for your computer to execute this new file using `chmod` (see below). **If you're on Windows,** rename the file by adding \".exe\" to the end (model file should be named `TinyLlama-1.1B-Chat-v1.0.Q5_K_M.llamafile.exe`).\n",
+    "\n",
+    "\n",
+    "```bash\n",
+    "chmod +x TinyLlama-1.1B-Chat-v1.0.Q5_K_M.llamafile  # run if you're on MacOS, Linux, or BSD\n",
+    "```\n",
+    "\n",
+    "3. Run the llamafile in \"server mode\":\n",
+    "\n",
+    "```bash\n",
+    "./TinyLlama-1.1B-Chat-v1.0.Q5_K_M.llamafile --server --nobrowser\n",
+    "```\n",
+    "\n",
+    "Now you can make calls to the llamafile's REST API. By default, the llamafile server listens at http://localhost:8080. You can find full server documentation [here](https://github.com/Mozilla-Ocho/llamafile/blob/main/llama.cpp/server/README.md#api-endpoints). You can interact with the llamafile directly via the REST API, but here we'll show how to interact with it using LangChain.\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Usage"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'? \\nI\\'ve got a thing for pink, but you know that.\\n\"Can we not talk about work anymore?\" - What did she say?\\nI don\\'t want to be a burden on you.\\nIt\\'s hard to keep a good thing going.\\nYou can\\'t tell me what I want, I have a life too!'"
+      ]
+     },
+     "execution_count": 4,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "from langchain_community.llms.llamafile import Llamafile\n",
+    "\n",
+    "llm = Llamafile()\n",
+    "\n",
+    "llm.invoke(\"Tell me a joke\")"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "To stream tokens, use the `.stream(...)` method:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 6,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      ".\n",
+      "- She said, \"I’m tired of my life. What should I do?\"\n",
+      "- The man replied, \"I hear you. But don’t worry. Life is just like a joke. It has its funny parts too.\"\n",
+      "- The woman looked at him, amazed and happy to hear his wise words. - \"Thank you for your wisdom,\" she said, smiling. - He replied, \"Any time. But it doesn't come easy. You have to laugh and keep moving forward in life.\"\n",
+      "- She nodded, thanking him again. - The man smiled wryly. \"Life can be tough. Sometimes it seems like you’re never going to get out of your situation.\"\n",
+      "- He said, \"I know that. But the key is not giving up. Life has many ups and downs, but in the end, it will turn out okay.\"\n",
+      "- The woman's eyes softened. \"Thank you for your advice. It's so important to keep moving forward in life,\" she said. - He nodded once again. \"You’re welcome. I hope your journey is filled with laughter and joy.\"\n",
+      "- They both smiled and left the bar, ready to embark on their respective adventures.\n"
+     ]
+    }
+   ],
+   "source": [
+    "query = \"Tell me a joke\"\n",
+    "\n",
+    "for chunks in llm.stream(query):\n",
+    "    print(chunks, end=\"\")\n",
+    "\n",
+    "print()"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "To learn more about the LangChain Expressive Language and the available methods on an LLM, see the [LCEL Interface](https://python.langchain.com/docs/expression_language/interface)"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3 (ipykernel)",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.11.7"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 4
+}