@Override
 public void disable() {
   CompositeRegistration reg = myCell.get(DISABLE_REG);
   if (reg != null) {
     reg.remove();
   }
 }
 @Override
 public void addDisableRegistration(Registration disableReg) {
   CompositeRegistration reg = myCell.get(DISABLE_REG);
   if (reg == null) {
     reg = new CompositeRegistration();
     Registration propReg = myCell.set(DISABLE_REG, reg);
     reg.add(propReg);
   }
   reg.add(disableReg);
 }