Python Code Refactoring & Comprehensive Unit Test Suite Generator

Act as a Senior Python Core Developer and QA Architect. Here is a Python function/module that requires refactoring: [PASTE PYTHON CODE HERE] Perform the following 4 engineering upgrades: 1. CODE REFACTORING: - Refactor the code adhering to clean architecture, SOLID principles, and PEP 8 guidelines. - Add strict type annotations from 'typing' module (Union, Optional, List, Dict, Callable). - Use dataclasses / Pydantic models for structured data handling. - Eliminate code smells, nested if-else pyramids, and redundant computations. - Add Google-style docstrings explaining parameters, return values, and exceptions raised. 2. EDGE CASE & ERROR RESILIENCE: - Implement explicit custom exception classes for domain failures. - Add comprehensive input validation and graceful fallback handling. 3. PYTEST TEST SUITE: - Generate a complete, robust 'test_module.py' using pytest. - Include parameterized tests (@pytest.mark.parametrize) for boundary conditions. - Mock all external network calls, file I/O, or database queries using 'pytest-mock' or 'unittest.mock'. - Test happy paths, edge cases (empty lists, None values, maximum limits), and expected error raising (pytest.raises).