code: @SuppressWarnings("unchecked")
      protected Set _transform(final Set set) {
          if (set == null) return null;
          if (set instanceof BeanSet) return set;
          return new BeanSet<>(set, this);
      }
docs: <p>_transform.</p>
  
  @param set a {@link java.util.Set} object.
  @return a {@link java.util.Set} object.