Using LangChain with Llama 2 | Generative AI Series

Updated on December 19, 2023

Introduction

Langchain is an Artificial Intelligence (AI) framework that simplifies coding when creating apps that implement external data sources and Large Language Models(LLMs).

You can use the framework to create personal assistants, chatbots, Q&A applications, and more. Langchain ships with different libraries that allow you to interact with various data sources like PDFs, spreadsheets, and databases (For instance, Chroma, Pinecone, Milvus, and Weaviate).

Chroma is an open-source embedding database that accelerates building LLM apps that require storing vector data and performing semantic searches.

In this guide, you'll implement the Langchain framework to orchestrate LLMs with a Chroma database.

Prerequisites

Before you begin:

Deploy a new Ubuntu 22.04 A100 Vultr Cloud GPU Server with at least:
- 80 GB GPU RAM
- 12 vCPUs
- 120 GB Memory
Establish an SSH connection to the server.
Create a non-root user with sudo rights and switch to the account.
Create a HuggingFace account.
Create a Hugging Face user access token.

Install the Required Python Libraries

You need to install the following Python libraries. Later on this guide, you'll run some Python scripts that use the libraries to work:

                            console
                            
                        
$ sudo apt update
$ pip install huggingface-hub pypdf langchain text_generation sentence-transformers chromadb gradio 
$ pip install -U jinja2

Run the Hugging Face Text Generation Inference Container

This guide requires Llama 2 model API. You'll expose the API by running the Hugging Face text generation inference Docker container. Follow the steps below:

Initialize the Docker container variables. Replace $HF_TOKEN with your correct Hugging Face token.
console
```
$ model=meta-llama/Llama-2-7b-chat-hf
volume=$PWD/data
token=$HF_TOKEN
```

Run the Hugging Face text generation Docker container.

                            console
                            
                        
$ sudo docker run -d  \
--name hf-tgi  \
--runtime=nvidia  \
--gpus all  \
-e HUGGING_FACE_HUB_TOKEN=$token  \
-p 8080:80  \
-v $volume:/data  \
ghcr.io/huggingface/text-generation-inference:1.1.0  \
--cuda-memory-fraction 0.5  \
--model-id $model  \
--max-input-length 2048  \
--max-total-tokens 4096

Wait for the container to download and load. Then, check the logs to ensure the container listens for incoming connections.
console
```
$ sudo docker logs -f hf-tgi
```

Ensure you get the following output.

Status: Downloaded newer image for ghcr.io/huggingface/text-generation-inference:1.1.0
c820c75b4a29ebff7a889443e65305bbf2b632b9299ffc6f3d445353ac1dbbd4

Implement a Basic Langchain Script

Follow the steps below to create a sample Langchain application to generate a query based on a prompt:

Create a new langchain-llama.py file using a text editor like nano.
console
```
$ nano langchain-llama.py
```

Enter the following information into the langchain-llama.py file.

                            python
                            
from langchain.llms import HuggingFaceTextGenInference

import warnings
warnings.simplefilter('ignore')

URI = "http://127.0.0.1:8080/"

llm = HuggingFaceTextGenInference(inference_server_url = URI)

print(llm("What is the capital of France?").strip())

Save and close the file.

Run the file.

console

$ python3 langchain-llama.py

Output:

The capital of France is Paris.

Prompt a Langchain Application

The Langchain framework accepts LLM prompts. Incorporate the prompt in your Python code by following the steps below:

Open a new langchain-llama-prompt.py file.
console
```
$ nano langchain-llama-prompt.py
```

Enter the following information into the langchain-llama-prompt.py file.

                            python
                            
                        
from langchain.llms import HuggingFaceTextGenInference
from langchain.llms import HuggingFaceTextGenInference
from langchain import PromptTemplate
from langchain.schema import StrOutputParser

import warnings
warnings.simplefilter('ignore')

URI = "http://127.0.0.1:8080/"
llm = HuggingFaceTextGenInference(inference_server_url = URI)

template = """
    <s>[INST] <<SYS>>
    {role}
    <</SYS>>       
    {text} [/INST]
"""

prompt = PromptTemplate(
    input_variables = [
        "role", 
        "text"
    ],
    template = template,
)

role = "Act as a Machine Learning engineer who is teaching high school students."

text = "Explain what is artificial intelligence in 2-3 sentences"

print(prompt.format(role = role, text = text))

chain = prompt | llm | StrOutputParser()

print(chain.invoke({"role": role,"text":text}))

Save and close the file.

Run the file

console

$ python3 langchain-llama-prompt.py

Output:

Hey there, young minds! *excited tone* Artificial intelligence (AI) is like a superhero for computers - it gives them the power to think and learn like humans! AI is a field of computer science that focuses on creating machines that can perform tasks that typically require human intelligence, like recognizing images, understanding speech, and making decisions. Just like how superheroes have special powers, AI algorithms have the ability to learn from data and improve their performance over time! 💻🦸‍♂️

Integrate Langchain with Chroma Database and Llama 2 Model

In this step, you'll use a sample speech from Steve Jobs and integrate Langchain with a Chroma database. Follow the steps below:

Download the sample PDF file using the Linux wget command:

console

$ wget https://docs.vultr.com/public/doc-assets/new/using-langchain-with-llama-2-generative-ai-series/steve-jobs.pdf

Open a new langchain_chroma.py file.
console
```
$ nano langchain_chroma.py
```

Enter the following information into the langchain_chroma.py file.

                            python
                            
                        
from pypdf import PdfReader
from langchain.llms import HuggingFaceTextGenInference
from langchain.embeddings import HuggingFaceEmbeddings
from langchain.chains.question_answering import load_qa_chain
from langchain.schema.runnable import RunnablePassthrough
from langchain.prompts import PromptTemplate
from langchain.document_loaders import PyPDFLoader
from langchain.text_splitter import CharacterTextSplitter
from langchain.vectorstores import Chroma
from langchain.schema import StrOutputParser
import joblib
import os

import warnings
warnings.filterwarnings('ignore')

URI      = "http://127.0.0.1:8080/"
model_id = "meta-llama/Llama-2-13b-chat-hf"
llm      = HuggingFaceTextGenInference(inference_server_url = URI, max_new_tokens = 2000)

template = """
<s>[INST] <<SYS>>
You are a helpful AI assistant.
Answer based on the context provided. If you cannot find the correct answer, say I don't know. Be concise and just include the response.
<</SYS>>
{context}
Question: {question}
Helpful Answer: [/INST]
"""

prompt = PromptTemplate.from_template(template)
reader = PdfReader('steve-jobs.pdf')

raw_text = ''

for i, page in enumerate(reader.pages):
    text = page.extract_text()
    if text:
        raw_text += text

text_splitter = CharacterTextSplitter(        
    separator       = " \n",
    chunk_size      = 500,
    chunk_overlap   = 20,
    length_function = len,
)
texts = text_splitter.split_text(raw_text)

texts[1]

embeddings_file = "./data/steve-jobs.joblib"

if os.path.exists(embeddings_file):
    embeddings = joblib.load(embeddings_file)
else:
    embeddings = HuggingFaceEmbeddings()
    joblib.dump(embeddings, embeddings_file)

vectorstore = Chroma.from_texts(texts, embeddings)

retriever = vectorstore.as_retriever()

chain = (
    {"context": retriever, "question": RunnablePassthrough()} 
    | prompt 
    | llm 
)

query = "Where did Steve Jobs deliver this speech?"

retriever.get_relevant_documents(query)

print(chain.invoke(query))

Save and close the file.

Run the file.

console

$ python3 langchain_chroma.py

Output:

Steve Jobs delivered this speech at Stanford University in 2005.

Creating a Q&A Application with Langchain and LLama 2 Model

Langchain has a built-in library for creating professional-looking user interfaces for chats. Follow the steps below to create a Web interface for your application:

Create a new chatbot.py file.
console
```
$ nano chatbot.py
```

Enter the following information into the chatbot.py file.

                            python
                            
                        
from pypdf import PdfReader
from langchain.llms import HuggingFaceTextGenInference
from langchain.embeddings import HuggingFaceEmbeddings
from langchain.vectorstores import Chroma
from langchain.schema.runnable import RunnablePassthrough
from langchain.prompts import PromptTemplate
from langchain.text_splitter import CharacterTextSplitter
import joblib
import os
import gradio as gr
import warnings

# Suppress warnings
warnings.filterwarnings('ignore')

# Constants
URI      = "http://127.0.0.1:8080/"
MODEL_ID = "meta-llama/Llama-2-13b-chat-hf"
EMBEDDINGS_FILE = "./data/steve-jobs.joblib"
PDF_FILE = 'steve-jobs.pdf'
TEMPLATE = """
    <s>[INST] <<SYS>>
    You are a helpful AI assistant.
    Answer based on the context provided. If you cannot find the correct answer, say I don't know. Be concise and just include the response.
    <</SYS>>
    {context}
    Question: {question}
    Helpful Answer: [/INST]
"""

# Initialize large language model
llm = HuggingFaceTextGenInference(inference_server_url = URI, max_new_tokens = 2000)

# Create a prompt template
prompt = PromptTemplate.from_template(TEMPLATE)

# Function to read and extract text from PDF
def extract_text_from_pdf(pdf_file):

    reader = PdfReader(pdf_file)
    raw_text = ''

    for page in reader.pages:
        text = page.extract_text()
        if text:
            raw_text += text
    return raw_text

# Function to get or create embeddings
def get_or_create_embeddings(texts, embeddings_file):

    if os.path.exists(embeddings_file):
        return joblib.load(embeddings_file)
    embeddings = HuggingFaceEmbeddings()
    joblib.dump(embeddings, embeddings_file)
    return embeddings

# Main chatbot function
def mychatbot(query, history):

    raw_text      = extract_text_from_pdf(PDF_FILE)
    text_splitter = CharacterTextSplitter(separator=" \n", chunk_size=500, chunk_overlap=20, length_function=len)
    texts = text_splitter.split_text(raw_text)

    embeddings  = get_or_create_embeddings(texts, EMBEDDINGS_FILE)
    vectorstore = Chroma.from_texts(texts, embeddings)
    retriever   = vectorstore.as_retriever()

    retriever.get_relevant_documents(query)
    chain = ({"context": retriever, "question": RunnablePassthrough()} | prompt | llm)
    return chain.invoke(query)

# Gradio interface setup
gr.ChatInterface(
    mychatbot,
    chatbot     = gr.Chatbot(height = 300),
    textbox     = gr.Textbox(placeholder="Ask me a question", container   = False, scale = 7),
    title       = "My Chatbot",
    description = "Custom Chatbot for your PDF",
    theme       = "soft",
    examples    = [
        "Where did Steve Jobs deliver this speech?",
        "Where did Steve Jobs start Apple?",
        "Apart from Apple, which other companies were founded by Steve Jobs?",
        "What was the bible of Steve Jobs?",
        "Who created the The Whole Earth Catalog and when?",
        "What was in The Whole Earth Catalog?",
        "What are the 3 key takeaways from Steve Jobs speech?",
    ],
    cache_examples = False,
    retry_btn      = None,
    undo_btn       = "Delete Previous",
    clear_btn      = "Clear"
).launch(share = True)

Save and close the file.

Run the file.

console

$ python3 chatbot.py

Output:

Running on local URL:  http://127.0.0.1:7860
Running on public URL: https://860a379e601450d71e.gradio.live

This share link expires in 72 hours. For free permanent hosting and GPU upgrades, run `gradio deploy` from Terminal to deploy to Spaces (https://huggingface.co/spaces)

Access the web interface by navigating to the public URL mentioned in the output.

Conclusion

In this guide, you have implemented the Langchain framework to orchestrate LLMs with the Chroma vector database. You've also created a chatbot using Chroma that exposes the functionalities of the Llama 2 model in a web interface.

Next Article: Fine-Tuning Llama 2 | Generative AI Series

Browse Learning Path:

Using LangChain with Llama 2 | Generative AI Series

Introduction

Prerequisites

Install the Required Python Libraries

Run the Hugging Face Text Generation Inference Container

Implement a Basic Langchain Script

Prompt a Langchain Application

Integrate Langchain with Chroma Database and Llama 2 Model

Creating a Q&A Application with Langchain and LLama 2 Model

Conclusion

Products

Features

Marketplace

Resources

Company