## Code Review #647
Description
Code Review
This pull request introduces several significant and beneficial changes to make the library more flexible and robust. Key changes include removing the enforced ChatMessageRole, renaming ChatMessage to Message, and using constants for JSON keys to reduce message size. The test coverage has been significantly improved, including a new test for the example, which is excellent. My review focuses on some opportunities to improve code clarity and leverage more modern Dart features, such as using const constructors for immutable classes and refactoring switch statements/expressions for better readability. Overall, this is a solid pull request that improves the library's design and usability.
Originally posted by @gemini-code-assist[bot] in #644 (review)