This is a package, currently under production, that allow the use of gyrovectors and gyrogroups in lean. These can be used to define general relativity, and they will be, eventually (my lecturers will be proud I'm finally doing some applied mathematics).
Look at my project board, it should be kept relatively up to date. If you feel the need to note the lack of up-to-dateness, find me on twitter or the zulip chat (its where I can usually be found).
Yes, thats what I thought. It sounds so very cool right? Once I've started this part of the project I'll write more about what exactly I'm doing with it.