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Building a Pairwise LLM Judge with Instructor and Pydantic

In this blog post, we'll explore how to create a pairwise LLM judge using Instructor and Pydantic. This judge will evaluate the relevance between a question and a piece of text, demonstrating a practical application of structured outputs in language model interactions.

Introduction

Evaluating text relevance is a common task in natural language processing and information retrieval. By leveraging large language models (LLMs) and structured outputs, we can create a system that judges the similarity or relevance between a question and a given text.

OpenAI API Model Distillation with Instructor

OpenAI has recently introduced a new feature called API Model Distillation, which allows developers to create custom models tailored to their specific use cases. This feature is particularly powerful when combined with Instructor's structured output capabilities. In this post, we'll explore how to leverage API Model Distillation with Instructor to create more efficient and specialized models.

Bad Schemas could break your LLM Structured Outputs

You might be leaving up to 60% performance gains on the table with the wrong response model. Response Models impact model performance massively with Claude and GPT-4o, irregardless of you’re using JSON mode or Tool Calling.

Using the right response model can help ensure your models respond in the right language or prevent hallucinations when extracting video timestamps.

We decided to investigate this by benchmarking Claude and GPT-4o on the GSM8k dataset and found that

  1. Field Naming drastically impacts performance - Changing a single field name from final_choice to answer improved model accuracy from 4.5% to 95%. The way we structure and name fields in our response models can fundamentally alter how the model interprets and responds to queries.
  2. Chain Of Thought significantly boosts performance - Adding a reasoning field increased model accuracy by 60% on the GSM8k dataset. Models perform significantly better when they explain their logic step-by-step.
  3. Be careful with JSON mode - JSON mode exhibited 50% more performance variation than Tool Calling when renaming fields. Different response models showed varying levels of performance between JSON mode and Tool Calling, indicating that JSON mode requires more careful optimisation.

Ensuring Consistent Timestamp Formats with Language Models

Gemini can Understand timestamps in language model outputs, but they can be inconsistent. Video content timestamps vary between HH:MM:SS and MM:SS formats, causing parsing errors and calculations. This post presents a technique to handle timestamps for clips and films without formatting issues.

We combine Pydantic's data validation with custom parsing for consistent timestamp handling. You'll learn to process timestamps in any format, reducing errors in video content workflows. Kinda like how we ensured matching language in multilingal summarization by adding a simple field.

The post provides a solution using Pydantic to improve timestamp handling in language model projects. This method addresses format inconsistencies and enables timestamp processing.

Instructor Proposal: Integrating Jinja Templating

As the creator of Instructor, I've always aimed to keep our product development streamlined and avoid unnecessary complexity. However, I'm now convinced that it's time to incorporate better templating into our data structure, specifically by integrating Jinja.

This decision serves multiple purposes:

  1. It addresses the growing complexity in my prompt formatting needs
  2. It allows us to differentiate ourselves from the standard library while adding proven utility.
  3. It aligns with the practices I've consistently employed in both production and client code.
  4. It provides an opportunity to introduce API changes that have been tested in private versions of Instructor.

Why Jinja is the Right Choice

  1. Formatting Capabilities
  2. Prompt formatting complexity has increased.
  3. List iteration and conditional implementation are necessary for formatting.
  4. This improves chunk generation, few shots, and dynamic rules.

  5. Validation

  6. Jinja template variables serve rendering and validation purposes.
  7. Pydantic's validation context allows access to template variables in validation functions.

  8. Versioning and Logging

  9. Render variable separation enhances prompt versioning and logging.
  10. Template variable diffing simplifies prompt change comparisons.

By integrating Jinja into Instructor, we're not just adding a feature; we're enhancing our ability to handle complex formatting, improve validation processes, and streamline our versioning and logging capabilities. This addition will significantly boost the power and flexibility of Instructor, making it an even more robust tool for our users.

Enhancing Formatting Capabilities

In Instructor, we propose implementing a new context keyword in our create methods. This addition will allow users to render the prompt using a provided context, leveraging Jinja's templating capabilities. Here's how it would work:

  1. Users pass a context dictionary to the create method.
  2. The prompt template, written in Jinja syntax, is defined in the content field of the message.
  3. Instructor renders the prompt using the provided context, filling in the template variables.

This approach offers these benefits:

  • Separation of prompt structure and dynamic content
  • Management of complex prompts with conditionals and loops
  • Reusability of prompt templates across different contexts

Let's look at an example to illustrate this feature:

client.create(
    model="gpt-4o",
    messages=[
        {
            "role": "user", 
            "content": """
                You are a {{ role }} tasks with the following question 

                <question>
                {{ question }}
                </question>

                Use the following context to answer the question, make sure to return [id] for every citation:

                <context>
                {% for chunk in context %}
                  <context_chunk>
                    <id>{{ chunk.id }}</id>
                    <text>{{ chunk.text }}</text>
                  </context_chunk>
                {% endfor %}
                </context>

                {% if rules %}
                Make sure to follow these rules:

                {% for rule in rules %}
                  * {{ rule }}
                {% endfor %}
                {% endif %}
            """
        },
    ],
    context={
        "role": "professional educator", 
        "question": "What is the capital of France?", 
        "context": [
            {"id": 1, "text": "Paris is the capital of France."}, 
            {"id": 2, "text": "France is a country in Europe."}
        ], 
        "rules": ["Use markdown."]
    }
)

Validation

Let's consider a scenario where we redact words from text. By using ValidationInfo to access context and passing it to the validator and template, we can implement a system for handling sensitive information. This approach allows us to:

  1. Validate input to ensure it doesn't contain banned words.
  2. Redact patterns using regular expressions.
  3. Provide instructions to the language model about word usage restrictions.

Here's an example demonstrating this concept using Pydantic validators:

from pydantic import BaseModel, ValidationInfo, field_validator

class Response(BaseModel):
    text: str

    @field_validator('text')
    @classmethod
    def no_banned_words(cls, v: str, info: ValidationInfo):
        context = info.context
        if context:
            banned_words = context.get('banned_words', set())
            banned_words_found = [word for word in banned_words if word.lower() in v.lower()]
            if banned_words_found:
                raise ValueError(f"Banned words found in text: {', '.join(banned_words_found)}, rewrite it but just without the banned words")
        return v

    @field_validator('text')
    @classmethod
    def redact_regex(cls, v: str, info: ValidationInfo):
        context = info.context
        if context:
            redact_patterns = context.get('redact_patterns', [])
            for pattern in redact_patterns:
                v = re.sub(pattern, '****', v)
        return v

response = client.create(
    model="gpt-4o",
    response_model=Response,
    messages=[
        {
            "role": "user", 
            "content": """
                Write about a {{ topic }}

                {% if banned_words %}
                You must not use the following banned words:

                <banned_words>
                {% for word in banned_words %}
                * {{ word }}
                {% endfor %}
                </banned_words>
                {% endif %}
              """
        },
    ],
    context={
        "topic": "jason and now his phone number is 123-456-7890"
        "banned_words": ["jason"],
        "redact_patterns": [
            r"\b\d{3}[-.]?\d{3}[-.]?\d{4}\b",  # Phone number pattern
            r"\b\d{3}-\d{2}-\d{4}\b",          # SSN pattern
        ],
    },
    max_retries=3,
)

print(response.text)
# > While i can't say his name anymore, his phone number is ****

Better Versioning and Logging

With the separation of prompt templates and variables, we gain several advantages:

  1. Version Control: We can now version the templates and retrieve the appropriate one for a given prompt. This allows for better management of template history, diffing and comparison.

  2. Enhanced Logging: The separation facilitates structured logging, enabling easier debugging and integration with various logging sinks, databases, and observability tools like OpenTelemetry.

  3. Security: Sensitive information in variables can be handled separately from the templates, allowing for better access control and data protection.

This separation of concerns adheres to best practices in software design, resulting in a more maintainable, scalable, and robust system for managing prompts and their associated data.

Side effect of Context also being Pydantic Models

Since they are just python objects we can use Pydantic models to validate the context and also control how they are rendered, so even secret information can be dynamically rendered! Consider using secret string to pass in sensitive information to the llm.

from pydantic import BaseModel, SecretStr

class UserContext(BaseModel):
    name: str
    address: SecretStr

class Address(BaseModel):
    street: SecretStr
    city: str
    state: str
    zipcode: str

def normalize_address(address: Address):
  context = UserContext(username="scolvin", address=address)
  address = client.create(
      model="gpt-4o",
      messages=[
          {
              "role": "user", 
              "content": "{{ user.name }} is `{{ user.address.get_secret_value() }}`, normalize it to an address object"
          },
      ],
      context={"user": context},
  )
  print(context)
  # > UserContext(username='jliu', address="******")
  print(address)
  # > Address(street='******', city="Toronto", state="Ontario", zipcode="M5A 0J3")
  logger.info(f"Normalized address: {address}", extra={"user_context": context, "address": address})
  return address

This approach offers several advantages:

  1. Secure logging: You can confidently log your template variables without risking the exposure of sensitive information.
  2. Type safety: Pydantic models provide type checking and validation, reducing the risk of errors.
  3. Flexibility: You can easily control how different types of data are displayed or used in templates.

Why should I use prompt caching?

Developers often face two key challenges when working with large context - Slow response times and high costs. This is especially true when we're making multiple of these calls over time, severely impacting the cost and latency of our applications. With Anthropic's new prompt caching feature, we can easily solve both of these issues.

Since the new feature is still in beta, we're going to wait for it to be generally avaliable before we integrate it into instructor. In the meantime, we've put together a quickstart guide on how to use the feature in your own applications.

Structured Outputs for Gemini now supported

We're excited to announce that instructor now supports structured outputs using tool calling for both the Gemini SDK and the VertexAI SDK.

A special shoutout to Sonal for his contributions to the Gemini Tool Calling support.

Let's walk through a simple example of how to use these new features

Installation

To get started, install the latest version of instructor. Depending on whether you're using Gemini or VertexAI, you should install the following:

pip install "instructor[google-generativeai]"
pip install "instructor[vertexai]"

This ensures that you have the necessary dependencies to use the Gemini or VertexAI SDKs with instructor.

We recommend using the Gemini SDK over the VertexAI SDK for two main reasons.

  1. Compared to the VertexAI SDK, the Gemini SDK comes with a free daily quota of 1.5 billion tokens to use for developers.
  2. The Gemini SDK is significantly easier to setup, all you need is a GOOGLE_API_KEY that you can generate in your GCP console. THe VertexAI SDK on the other hand requires a credentials.json file or an OAuth integration to use.

Getting Started

With our provider agnostic API, you can use the same interface to interact with both SDKs, the only thing that changes here is how we initialise the client itself.

Before running the following code, you'll need to make sure that you have your Gemini API Key set in your shell under the alias GOOGLE_API_KEY.

import instructor
import google.generativeai as genai
from pydantic import BaseModel


class User(BaseModel):
    name: str
    age: int


client = instructor.from_gemini(
    client=genai.GenerativeModel(
        model_name="models/gemini-1.5-flash-latest", # (1)!
    )
)

resp = client.chat.completions.create(
    messages=[
        {
            "role": "user",
            "content": "Extract Jason is 25 years old.",
        }
    ],
    response_model=User,
)

print(resp)
#> name='Jason' age=25
  1. Current Gemini models that support tool calling are gemini-1.5-flash-latest and gemini-1.5-pro-latest.

We can achieve a similar thing with the VertexAI SDK. For this to work, you'll need to authenticate to VertexAI.

There are some instructions here but the easiest way I found was to simply download the GCloud cli and run gcloud auth application-default login.

import instructor
import vertexai  # type: ignore
from vertexai.generative_models import GenerativeModel  # type: ignore
from pydantic import BaseModel

vertexai.init()


class User(BaseModel):
    name: str
    age: int


client = instructor.from_vertexai(
    client=GenerativeModel("gemini-1.5-pro-preview-0409"), # (1)!
)


resp = client.chat.completions.create(
    messages=[
        {
            "role": "user",
            "content": "Extract Jason is 25 years old.",
        }
    ],
    response_model=User,
)

print(resp)
#> name='Jason' age=25
  1. Current Gemini models that support tool calling are gemini-1.5-flash-latest and gemini-1.5-pro-latest.