Implement schema constraints for OpenAI

[GirinMan]

Description

Implements schema constraints for OpenAI models, enabling structured outputs with JSON format without requiring output fencing.

Fixes #59

Feature

How Has This Been Tested?

Comprehensive testing has been performed through automated tests and code review:

Tests Added

1. Unit Tests (tests/inference_test.py)

• test_openai_schema_constraints_json: Validates that schema constraints work correctly with JSON format
• test_openai_schema_constraints_yaml_raises_error: Ensures YAML format with schema constraints raises appropriate error
• test_openai_with_schema_constraints: Verifies correct API parameters are sent to OpenAI when using structured outputs

2. Schema Tests (tests/schema_test.py)

• OpenAISchemaTest class with multiple test cases:
  • Tests schema generation from empty extractions
  • Tests schema generation with and without attributes
  • Tests handling of list-type attributes
  • Tests custom attribute suffix functionality

3. Integration Tests (tests/openai_extract_test.py)

• test_extract_with_openai_schema_constraints: End-to-end test of extract() function with OpenAI schema constraints
• test_extract_openai_yaml_with_schema_raises_error: Validates error handling for unsupported YAML format
• test_extract_openai_fence_output_with_schema_raises_error: Validates error handling for fence_output=True
• test_extract_openai_without_schema_constraints: Ensures backward compatibility

Test Coverage

• Schema generation and validation
• API parameter construction with response_format
• Error handling for unsupported configurations
• Backward compatibility for existing functionality

Running Tests

Command:

$ pytest tests/inference_test.py
$ pytest tests/schema_test.py
$ pytest tests/openai_extract_test.py

Note: The tests use mocked OpenAI API responses to avoid requiring actual API keys during testing.

Checklist:

• I have read and acknowledged Google's Open Source Code of conduct.
• I have read the Contributing page, and I either signed the Google Individual CLA or am covered by my company's Corporate CLA.
• I have discussed my proposed solution with code owners in the linked issue(s) and we have agreed upon the general approach.
• I have made any needed documentation changes, or noted in the linked issue(s) that documentation elsewhere needs updating.
• I have added tests, or I have ensured existing tests cover the changes
• I have followed Google's Python Style Guide and ran pylint over the affected code.

[github-actions]

Manual validation results:

Size: 798 lines
Template: ✓
Linked issue: ✓

Run ID: 16790875474

[github-actions]

Manual validation results:

Size: 798 lines
Template: ✓
Linked issue: ✓

Run ID: 16791196611

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Manual Validation Results

Status: ❌ Failed

Check	Status	Details
PR Size	✅	798 lines
Template	✅	Complete
Linked Issue	✅	Found

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Manual Validation Results

Status: ✅ Passed

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PR Size	✅	798 lines
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Linked Issue	✅	Found

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⚠️ Branch Update Required

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⚠️ Branch Update Required

Your branch is 86 commits behind main. Please update your branch to ensure CI checks run with the latest code:

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Note: Enable "Allow edits by maintainers" to allow automatic updates.