docs: public boolean add(T res) {
          if (_dupesChecker != null) {
              RepositoryResourceMatchingData matchingData = ((RepositoryResourceImpl) res).createMatchingData();
              if (!_dupesChecker.contains(matchingData)) {
                  _dupesChecker.add(matchingData);
                  _backingCollection.add(res);
                  return true;
              } else {
                  return false;
              }
          } else {
              _backingCollection.add(res);
              return true;
          }
      }