Add a couple more append operations
Add a couple more append operations

amaliujia/lenskit,vaibhav345/lenskit,vaibhav345/lenskit,vaibhav345/lenskit,tajinder-txstate/lenskit,vijayvani/Lenskit,vijayvani/Lenskit,blankazucenalg/lenskit,tajinder-txstate/lenskit,tajinder-txstate/lenskit,amaliujia/lenskit,chrysalag/lenskit,binweiwu/lenskit,martinlaz/lenskit,kluver/lenskit,aglne/lenskit,chrysalag/lenskit,martinlaz/lenskit,kluver/lenskit,binweiwu/lenskit,linjunleo/lenskit,aglne/lenskit,tajinder-txstate/lenskit,kluver/lenskit,kluver/lenskit,kluver/lenskit,blankazucenalg/lenskit,linjunleo/lenskit,vaibhav345/lenskit