[new_pymtl] add tests for slices
[new_pymtl] add tests for slices

jck/pymtl,Glyfina-Fernando/pymtl,Glyfina-Fernando/pymtl,cfelton/pymtl,jck/pymtl,12yujim/pymtl,jck/pymtl,cornell-brg/pymtl,cornell-brg/pymtl,jjffryan/pymtl,12yujim/pymtl,cfelton/pymtl,cornell-brg/pymtl,12yujim/pymtl,Glyfina-Fernando/pymtl,cfelton/pymtl,tj93/pymtl,tj93/pymtl,tj93/pymtl,jjffryan/pymtl,jjffryan/pymtl