public Object process(InvocableMap.Entry entry) {
   Vet vet = (Vet) entry.getValue();
   if (vet.getSpecialties().contains(specialty)) {
     return false;
   }
   vet.addSpecialty(specialty);
   return true;
 }
 @Override
 public Object process(InvocableMap.Entry entry) {
   Object value = entry.getValue();
   return condition.evaluate(value) ? value : null;
 }