- fmtlib: https://github.com/fmtlib/fmt (MIT license)
- pystring: https://github.com/imageworks/pystring (BSD 3-Clause "New" or "Revised" License)
- debugbreak: https://github.com/scottt/debugbreak/blob/master (BSD 2-Clause "Simplified" License)
- https://github.com/github/gitignore (Creative Commons Zero v1.0 Universal)
- doctest: https://github.com/doctest/doctest (MIT License)
- argh: https://github.com/adishavit/argh