Well again the code is nearly completely opaque to me (goes to show you that there is such a thing as too much abstraction) but again based off of the name "semi_implicit_integrate" it would be crazy for this to be anything but a Semi-Implicit Euler integrator. That falls into the class of symplectic integrators, so it should handle SE(3) fine.

There is also a explicit method in there, which probably won't handle it very well.

On the other hand, I hesitate to argue with the author about their own code... or are you just the OP?

I'm just an interested onlooker, yes.