code: public <T> List<Key<T>> getKeysByManualRefs(final Class<T> clazz, final List<Object> refs) {
          final String collection = getCollectionName(clazz);
          final List<Key<T>> keys = new ArrayList<Key<T>>(refs.size());
          for (final Object ref : refs) {
              keys.add(this.<T>manualRefToKey(collection, ref));
          }
  
          return keys;
      }
docs: Gets the Keys for a list of objects
  
  @param clazz the Class of the objects
  @param refs  the objects to fetch the keys for
  @param <T>   the type of the entity
  @return the list of Keys