Code Refactor for Speed and Readability

[pderrenger]

This Ultralytics PR refactors code to improve performance and readability. 🔄

Key changes include:

🚀 Optimized various functions for faster execution.
🧩 Simplified complex logic for better understanding and maintenance.
🗑️ Removed redundant code to streamline operations.
📚 Improved code structure and organization.

These changes aim to enhance the overall quality and efficiency of the code. 🌟

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

This PR implements minor improvements and fixes in YAML file handling and dataset construction within the YOLOv5 codebase.

📊 Key Changes

• Modified the yaml_save function to handle a None data parameter safely by initializing it as an empty dictionary.
• Refactored the construct_dataset function to streamline the creation of the data_dict used for dataset paths.

🎯 Purpose & Impact

• Ensures the yaml_save function can handle cases where no data is passed, preventing potential errors. 🛠️
• Simplifies the code in construct_dataset, making it more readable and maintainable. 📚

These changes improve the robustness and clarity of the code, benefiting both developers working on the codebase and users relying on these functionalities for their machine learning projects. 🧠