What's Changed
- Add instruction to build sdist in release script by @hcho3 in #462
- [CI] Use Python 3.8 by @hcho3 in #476
- Set type fields in ConcatenateModelObjects() by @hcho3 in #475
- Add API function to serialize to strings by @hcho3 in #480
Full Changelog: 3.2.0...3.3.0