Since there are two interface named detach and dettach in libvirt virsh (maybe some historycal reason), so I think our virsh module should follow the libvirt to expose two interface named detach and dettach.
Actually the two interface call the same function and does the same work in libvirt, so I build the two method in our virsh module doing the same work.

Since our virsh module is used to simulate virsh command, I prefer to build the same interface as what the libvirt expose.