code: public FilterValues<S> initialFilterValues() {
          FilterValues<S> filterValues = mFilterValues;
          if (filterValues == null) {
              buildFilterValues();
              filterValues = mFilterValues;
          }
          return filterValues;
      }
docs: Returns a FilterValues instance for assigning values to a
  Filter. Returns null if Filter has no parameters.
  
  <p>Note: The returned FilterValues instance may reference a different
  filter instance than this one. Call getFilter to retrieve it. The
  difference is caused by the filter property values being {@link #bind bound}.