code: public static List<Precedence> newPrecedence(Collection<VM> vmsBefore, Collection<VM> vmsAfter) {
          List<Precedence> l = new ArrayList<>(vmsBefore.size() * vmsAfter.size());
          for (VM vmb : vmsBefore) {
              for (VM vma : vmsAfter) {
                  l.add(new Precedence(vmb, vma));
              }
          }
          return l;
      }
docs: Instantiate discrete constraints to force a set of VMs to migrate after an other set of VMs.
  
  @param vmsBefore the VMs to migrate before the others {@see vmsAfter}
  @param vmsAfter  the VMs to migrate after the others {@see vmsBefore}
  @return the associated list of constraints