This pull request primarily improves the handling and serialization of keypoints and keypoints lists in the Capybara library, ensuring consistent formatting, better support in mixins, and more robust test coverage. The changes also include code style improvements for readability and maintainability.

Keypoints and KeypointsList Support

• Added Keypoints and KeypointsList to imports and serialization logic in dict_to_jsonable, allowing these types to be properly converted to JSON-friendly formats. [1] [2]
• Updated test cases to include Keypoints and KeypointsList objects, validating their serialization and ensuring compatibility with custom functions. [1] [2]

Code Style and Consistency

• Standardized string quotes from single to double across files for consistency. [1] [2]
• Refactored conditionals and error messages in the keypoints.py structures for clarity and uniformity. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]

Mixins Improvements

• Simplified methods and attributes in mixins, especially DataclassToJsonMixin, for easier usage and less boilerplate.
• Improved handling of custom serialization functions and parameter passing in mixins.

Test and Maintenance

• Enhanced test parameterization and updated test data for broader coverage, including new types and serialization scenarios. [1] [2]
• Minor cleanups in test and mixin files for better readability and maintainability. [1] [2] [3]

These changes collectively make the Capybara library more robust and easier to use, especially when working with keypoints data in serialization and testing workflows.