code: 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;
          }
      }
docs: Adds a resource to the collector.
  <p>
  If {@link DuplicatePolicy#FORBID_DUPLICATES} was passed to the constructor, the {@link RepositoryResourceMatchingData} of the resource will be compared to each resource in
  the collection. If a match is found, the new resource will not be added to the collector.
  
  @param res the resource to add to the collector
  @return true if the resource was successfully added to the collector, otherwise false