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The Plexe Python library (plexe) provides a powerful way to build machine learning models using natural language. Understanding these core concepts will help you use it effectively.

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Model (plexe.Model)

This is the central class you interact with. A Model object represents a machine learning task and, once built, the resulting trained model.
  • Initialization: You create a Model by specifying its intent and optionally its input_schema, output_schema, and constraints.
  • State: A Model progresses through states: DRAFT (initial), BUILDING (during build() call), READY (successfully built), ERROR (build failed).
  • Building: The build() method triggers the agentic workflow to generate, train, and evaluate the model based on the intent and provided data.
  • Prediction: The predict() method uses the trained model (once READY) to make predictions on new data.
  • Persistence: save_model() and load_model() allow you to store and retrieve trained models.

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Intent

The intent is a natural language string describing what you want the machine learning model to do. It’s the primary instruction given to the Plexe agent system.
  • Example: "Predict the likelihood of customer churn based on their recent activity and subscription plan."
  • Clarity is Key: A clear and specific intent leads to better model planning and results. Include context about the goal, inputs, and outputs if possible.

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Schemas (input_schema, output_schema)

Schemas define the structure and data types of the model’s expected inputs and outputs.
  • Purpose: They ensure data consistency and help the agents understand the data format.
  • Formats: Can be provided as Pydantic models (recommended) or Python dictionaries.
  • Inference: If not provided, Plexe attempts to infer schemas from the datasets supplied during the build call, using LLM analysis to identify the likely target variable(s). Explicitly defining schemas is often more reliable.

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Build Process (model.build())

This method orchestrates the core model creation workflow.
  • Inputs: Requires datasets (list of Pandas DataFrames or DatasetGenerator objects) and a provider configuration (LLM to use). Optional arguments include max_iterations, timeout, callbacks, etc.
  • Agent System (PlexeAgent): Internally, build invokes a multi-agent system (PlexeAgent) comprising specialized roles:
    • Orchestrator: Manages the overall workflow, delegating tasks.
    • ML Researcher: Analyzes the problem, proposes solution plans.
    • ML Engineer: Writes and refines the model training code based on the plan.
    • ML Ops Engineer: Generates the inference code for the final model.
    • (Tool Agents): Smaller, specialized agents perform tasks like metric selection, schema inference, code validation, and execution using defined “tools”.
  • Iteration: The system may try multiple approaches (max_iterations) to find the best model according to the selected performance metric. Each attempt involves planning, code generation, execution, and evaluation.
  • Output: Updates the Model object’s state (READY or ERROR), populates its predictor, metric, metadata, artifacts, and source code attributes.

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Provider (provider, ProviderConfig)

Specifies the Large Language Model(s) (LLMs) used by the agent system.
  • Simple String: "openai/gpt-4o-mini" or "anthropic/claude-3-haiku-20240307". Uses this model for most agent tasks.
  • ProviderConfig Object: Allows assigning different models to different agent roles (Orchestrator, Researcher, Engineer, Ops, Tool) for fine-grained control over cost and capability.
  • Dependencies: Relies on LiteLLM for multi-provider support. Requires appropriate API keys set as environment variables.

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Datasets (datasets, DatasetGenerator)

Data used for training and evaluation.
  • Input: Pass data to model.build() as a list containing Pandas DataFrames.
  • DatasetGenerator: A class (plexe.DatasetGenerator) can be used to define requirements for a dataset, including generating synthetic data based on a schema or augmenting existing data using an LLM provider. Pass instances of this class in the datasets list if needed.

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Callbacks (plexe.Callback, MLFlowCallback)

Classes that allow you to hook into the build() process lifecycle (on_build_start, on_iteration_start, on_iteration_end, on_build_end).
  • Purpose: Used for logging, monitoring, custom artifact handling, etc.
  • Built-in: Includes MLFlowCallback for easy integration with MLflow tracking. The ChainOfThoughtModelCallback provides verbose agent step logging when chain_of_thought=True is set in build().
  • Custom: You can create your own callbacks by inheriting from plexe.Callback.

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Constraints (plexe.Constraint)

Represents rules or conditions that a model’s input/output pairs should satisfy. Constraints enable you to specify business rules and validation criteria for your model’s behavior.
  • Definition: Create constraints with a condition function that takes input and output data and returns a boolean
  • Composability: Combine constraints using logical operators (& for AND, | for OR, ~ for NOT)
  • Usage Example: 
    # Constraint ensuring price predictions are positive
positive_price = Constraint(
    condition=lambda inputs, outputs: outputs["price"] > 0,
    description="Predicted prices must be positive"
)

# Constraint requiring predictions to have a confidence value
has_confidence = Constraint(
    condition=lambda inputs, outputs: "confidence" in outputs,
    description="Predictions must include a confidence score"
)

# Combined constraint
valid_model = positive_price & has_confidence

# Apply constraints when creating a model
model = Model(intent="...", constraints=[valid_model])