More up-to-date code with newer versions of Dart | Slightly Better Documentation

[psygo]

This is a minor refactoring featuring mostly — no behavior has changed —:

• Variables which could be final are now final.
• The Dart documentation, which was made with comments, now uses ///, conforming with the Dart docstrings.
• part statements have been replaced with exports, conforming to the recommendation on the package layout conventions.
• The changelog file now has upper case letters.

[whesse]

I see where the instructions you reference, https://dart.dev/guides/libraries/create-library-packages , suggest using "show" clauses in the public api of the library, but in this case, the library is small, and the classes are clearly visible in the generated API documentation, so I don't think it is worth it in this case.