Add some support of ONNX through codex

[pobonomo]

No description provided.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.

---

Pierre Bonami seems not to be a GitHub user. You need a GitHub account to be able to sign the CLA. If you have already a GitHub account, please add the email address used for this commit to your account.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[Copilot]

Pull Request Overview

This PR adds support for ONNX (Open Neural Network Exchange) models to gurobi-ml, enabling formulation of ONNX-based neural networks into Gurobi optimization models. The implementation focuses on sequential multi-layer perceptrons with Gemm/MatMul operations and ReLU activations, consistent with existing Keras and PyTorch support.

Key changes:

• New ONNX module with model parsing and constraint generation
• Test infrastructure for ONNX formulations and cross-framework equivalence testing
• Documentation updates and example notebook demonstrating adversarial attacks with ONNX models

Reviewed Changes

Copilot reviewed 12 out of 14 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tox.ini	Added ONNX test environments and dependencies to the test matrix
tests/test_onnx/test_onnx_formulations.py	Test cases for ONNX model formulations using Gemm and MatMul operations
tests/test_onnx/test_onnx_exceptions.py	Tests for unsupported ONNX operations
tests/test_composite/test_framework_onnx_equivalence.py	Cross-framework tests verifying ONNX conversions produce equivalent results
src/gurobi_ml/registered_predictors.py	Registered ONNX convertor with predictor registry
src/gurobi_ml/onnx/onnx_model.py	Core implementation of ONNX model parsing and Gurobi formulation
src/gurobi_ml/onnx/init.py	ONNX module initialization and exports
requirements.onnx.txt	ONNX package dependencies
notebooks/adversarial/adversarial_onnx.ipynb	Example notebook demonstrating adversarial attacks using ONNX
docs/source/user/supported.rst	Documentation for ONNX support
docs/source/index.rst	Updated framework list to include ONNX
docs/source/api.rst	Added ONNX API documentation section

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.