chore: import upstream snapshot with attribution

docs/agents/python.md

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+# Python Guidelines
+
+For Python providers, prompts, assertions, and scripts.
+
+## Requirements
+
+- Python 3.8 or later
+- Follow [Google Python Style Guide](https://google.github.io/styleguide/pyguide.html)
+- Use type hints for readability and error catching
+
+## Linting & Formatting
+
+Use `ruff` for both:
+
+```bash
+ruff check --fix           # Lint with auto-fix
+ruff check --select I --fix # Sort imports
+ruff format                 # Format code
+```
+
+## Testing
+
+Use the built-in `unittest` module for new Python tests.
+
+## Best Practices
+
+- Keep dependencies minimal - avoid unnecessary external packages
+- When adding examples, update relevant `requirements.txt` files
+- Follow promptfoo API patterns for custom providers/prompts/assertions
+- Write unit tests for new Python functions
+
+## Provider Pattern
+
+```python
+def call_api(prompt: str, options: dict, context: dict) -> dict:
+    """
+    Args:
+        prompt: The prompt string
+        options: Provider configuration
+        context: Variables from the test case
+
+    Returns:
+        dict with 'output' key (and optionally 'error')
+    """
+    # Implementation
+    return {"output": response_text}
+```
+
+## Assertion Pattern
+
+```python
+def get_assert(output: str, context: dict) -> dict:
+    """
+    Args:
+        output: The provider's output
+        context: Test context including vars
+
+    Returns:
+        dict with 'pass' (bool) and optionally 'reason'
+    """
+    return {"pass": True, "reason": "Validation passed"}
+```