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 "sem

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?